Opel Insignia: Diagnostic Information and Procedures

DTC C0126

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Refer to Diagnostic Procedure Instructions for an overview of each diagnostic category.

DTC Descriptor

DTC C0126

Brake Fluid Level Sensor Circuit

For symptom byte information refer to Symptom Byte List.

Diagnostic Fault Information

Circuit/System Description

The brake fluid level switch monitors the level of the brake fluid in the brake fluid reservoir. When the brake fluid level switch input closed, the electronic brake control module will set the DTC.

Conditions for Running the DTC

Ignition ON/Vehicle in Service Mode/Vehicle in Service Mode.

Conditions for Setting the DTC

• Low brake fluid level is detected for 5 s.
• An open is detected on the ground circuit.
• An open or short to voltage is detected on the signal circuit.

Action Taken When the DTC Sets

• The electronic brake control module disables the traction control and stability control for the duration of the ignition cycle.
• The traction control/stability control-active indicator turns ON.
• The brake warning indicator turns ON.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

Reference Information

Schematic Reference

Hydraulic Brake Wiring Schematics

Connector End View Reference

Component Connector End View Index

Description and Operation

Hydraulic Brake System Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Scan Tool Reference

Refer to Control Module References for scan tool information.

Circuit/System Verification

1. Verify that the brake fluid level is above the minimum level.

• If low

Refer to Brake Fluid Loss.

• Go to next step: If above minimum level

2. Refer to Circuit/System Testing.

Circuit/System Testing

1. Ignition OFF/Vehicle OFF and all vehicle systems OFF, disconnect the harness connector at the B20 Brake Fluid Level Switch. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 10 Ω between the ground circuit terminal 2 and ground.

• If 10 Ω or greater

1. Ignition OFF/Vehicle OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, repair the open/high resistance in the ground connection.

• Go to next step: If less than 10 Ω

3. Ignition ON/Vehicle in Service Mode.

4. Verify the scan tool Brake Fluid Level Sensor parameter is OK.

• If the parameter is not OK

1. Ignition OFF/Vehicle OFF/Vehicle OFF, disconnect the harness connector at the K17 Electronic Brake Control Module.
2. Test for infinite resistance between the signal circuit terminal 1 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the K17 Electronic Brake Control Module.

• Go to next step: If the parameter is OK

5. Ignition OFF/Vehicle OFF.

6. Install a 3 A fused jumper wire between the signal circuit terminal 1 and ground.

7. Ignition ON/Vehicle in Service Mode.

8. Verify the scan tool Brake Fluid Level Sensor parameter is Low.

• If the parameter is not Low

1. Ignition OFF/Vehicle OFF, disconnect the harness connector at the K17 Electronic Brake Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • Go to next step: If less than 1 V.
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K17 Electronic Brake Control Module.

• Go to next step: If the parameter is Low

9. Test or replace the B20 Brake Fluid Level Switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Refer to Control Module References for electronic brake control module replacement, programming and setup.

DTC C025E

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Refer to Diagnostic Procedure Instructions for an overview of each diagnostic category.

DTC Descriptor

DTC C025E

Brake Booster Vacuum Sensor Circuit

For symptom byte information refer to Symptom Byte List.

Diagnostic Fault Information

Circuit/System Description

The brake booster vacuum sensor monitors the pressure in the brake booster. The electronic brake control module supplies a 5 V reference and a low reference circuit to the brake booster vacuum sensor. The vacuum sensor supplies a voltage signal in relation to the pressure in the brake booster to the electronic brake control module.

Conditions for Running the DTC

C025E 00, C025E 01, C025E 06, C025E 1F

Ignition ON

C025E 5A

• Ignition ON.
• Brakes are not applied.

Conditions for Setting the DTC

C025E 00

• A short to ground is detected on the 5V reference circuit.
• A short to voltage is detected on the 5V reference circuit.

C025E 01

• A short to voltage is detected on the signal circuit.
• An open/high resistance is detected on the low reference circuit.

C025E 06

• An open/high is detected on the signal circuit.
• A short to ground is detected on the signal circuit.
• An open/high is detected on the 5V reference circuit.

C025E 1F

The vacuum sensor signal is erratic.

C025E 5A

The vacuum sensor signal is not plausible.

Action Taken When the DTC Sets

Service Brake Assist message is displayed on the driver information center

Conditions for Clearing the DTC

The DTC clears when the diagnostic runs and passes

Reference Information

Schematic Reference

Hydraulic Brake Wiring Schematics

Connector End View Reference

Component Connector End View Index

Description and Operation

Brake Assist System Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Refer to Control Module References for scan tool information

Circuit/System Verification

1. Verify that the brake booster vacuum system has no damage, leakage or incorrect installation.

• If damage, leakage or incorrect installation is found

Refer to Brake Assist System Diagnosis

• Go to next step: If no damage, leakage or incorrect installation is found

2. Refer to Circuit/System Testing.

Circuit/System Testing

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the B19B Brake Booster Vacuum Sensor. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 10 Ω between the low reference circuit terminal 2 and ground.

• If 10 Ω or greater

1. Disconnect the harness connector at the K17 Electronic Brake Control Module.
2. Test for less than 2 Ω in the low reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K17 Electronic Brake Control Module.

• Go to next step: If less than 10 Ω

3. Ignition ON.

4. Test for 4.8 - 5.2 V between the 5 V reference circuit terminal 3 and ground.

• If less than 4.8 V

1. Ignition OFF, disconnect the harness connector at the K17 Electronic Brake Control Module.
2. Test for infinite resistance between the 5 V reference circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the 5 V reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K17 Electronic Brake Control Module.

If greater than 5.2 V

1. Ignition OFF, disconnect the harness connector at the K17 Electronic Brake Control Module, ignition ON.
2. Test for less than 1 V between the 5 V reference circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K17 Electronic Brake Control Module.

• Go to next step: If between 4.8 - 5.2 V

5. Ignition OFF, disconnect the harness connector at the K17 Electronic Brake Control Module, Ignition ON.

6. Test for less than 1 V between the B19B Brake Booster Vacuum Sensor signal circuit terminal 1 and ground.

• If greater than 1 V

Repair the short to voltage on the circuit.

• Go to next step: If less than 1 V

7. Ignition OFF.

8. Test for infinite resistance between the B19B Brake Booster Vacuum Sensor signal circuit terminal 1 and ground.

• If less than infinite resistance

Repair the short to ground on the circuit.

• Go to next step: If infinite resistance

9. Test for less than 2 Ω between the B19B Brake Booster Vacuum Sensor signal circuit terminal 1 and the K17 Electronic Brake Control Module signal circuit terminal 34.

• If 2 Ω or greater

Repair the open/high resistance in the circuit.

• Go to next step: If less than 2 Ω

10. Test or replace the B19B Brake Booster Vacuum Sensor.

11. Verify the DTC does not set while operating the vehicle under Conditions for Running the DTC.

• If the DTC sets

Replace the K17 Electronic Brake Control Module.

• Go to next step: If the DTC does not set

12. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Refer to Power Brake Booster Vacuum Sensor Replacement (2.0L LTG) or Power Brake Booster Vacuum Sensor Replacement (3.6L LGX)
• Refer to Control Module References for electronic brake control module replacement, programming and setup

DTC C0267

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Refer to Diagnostic Procedure Instructions for an overview of each diagnostic category.

DTC Descriptor

DTC C0267

Low Brake Fluid Indicated

For symptom byte information refer to Symptom Byte List.

Diagnostic Fault Information

Circuit/System Description

The brake fluid level switch monitors the level of the brake fluid in the brake fluid reservoir. When the brake fluid level switch input closed, the electronic brake control module will set the DTC.

Conditions for Running the DTC

Ignition ON/Vehicle in Service Mode.

Conditions for Setting the DTC

Low brake fluid level is detected for 8 s.

Action Taken When the DTC Sets

• The electronic brake control module disables the traction control and stability control for the duration of the ignition cycle.
• The traction control/stability control-active indicator turns ON.
• The brake warning indicator turns ON.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

Reference Information

Schematic Reference

Hydraulic Brake Wiring Schematics

Connector End View Reference

Component Connector End View Index

Description and Operation

Brake Warning System Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Scan Tool Reference

Refer to Control Module References for scan tool information.

Circuit/System Verification

1. Verify that the brake is above minimum level.

• If low

Refer to Brake Fluid Loss.

• Go to next step: If above minimum level

Go to next step: Refer to Circuit/System Testing.

Circuit/System Testing

1. Ignition OFF/Vehicle OFF and all vehicle systems OFF, disconnect the harness connector at the B20 Brake Fluid Level Switch. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 10 Ω between the ground circuit terminal 2 and ground.

• If 10 Ω or greater

1. Ignition OFF/Vehicle OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, repair the open/high resistance in the ground connection.

• Go to next step: If less than 10 Ω

3. Ignition ON/Vehicle in Service Mode.

4. Verify the scan tool Brake Fluid Level Sensor parameter is OK.

• If the parameter is not OK

1. Ignition OFF/Vehicle OFF/Vehicle OFF, disconnect the harness connector at the K17 Electronic Brake Control Module.
2. Test for infinite resistance between the signal circuit terminal 1 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the K17 Electronic Brake Control Module.

• Go to next step: If the parameter is OK

5. Ignition OFF/Vehicle OFF.

6. Install a 3 A fused jumper wire between the signal circuit terminal 1 and ground.

7. Ignition ON/Vehicle in Service Mode.

8. Verify the scan tool Brake Fluid Level Sensor parameter is Low.

• If the parameter is not Low

1. Ignition OFF/Vehicle OFF, disconnect the harness connector at the K17 Electronic Brake Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • Go to next step: If less than 1 V.
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K17 Electronic Brake Control Module.

• Go to next step: If the parameter is Low

9. Test or replace the B20 Brake Fluid Level Switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Refer to Control Module References for electronic brake control module replacement, programming and setup.

DTC C0299

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Refer to Diagnostic Procedure Instructions for an overview of each diagnostic category.

DTC Descriptor

DTC C0299 56

Brake Booster Large Vacuum Leak Detected Too Many Transitions

Circuit/System Description

The brake booster vacuum sensor measures the vacuum in the brake booster assembly. The electronic brake control module supplies a 5 V reference and a low reference circuit to the brake booster vacuum sensor. The vacuum sensor supplies a voltage signal in relation to the pressure in the brake booster to the electronic brake control module.

Conditions for Running the DTC

Ignition ON.

Conditions for Setting the DTC

The EBCM detected a too low vacuum in the brake booster assembly for 120 s.

Action Taken When the DTC Sets

The brake warning indicator turns ON.

Conditions for Clearing the DTC

• A current DTC clears when the diagnostic runs and passes.
• The electronic brake control module will turn OFF the indicator in the next ignition cycle.

Reference Information

Schematic Reference

Hydraulic Brake Wiring Schematics

Connector End View Reference

Component Connector End View Index

Description and Operation

Brake Assist System Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Scan Tool Reference

Refer to Control Module References.

Circuit/System Testing

1. Ignition ON.

2. Verify that DTC C025E is not set.

• If the DTC is set

Refer to DTC C025E.

• Go to next step: If the DTC is not set

3. Verify that the brake booster vacuum system has no damage, leakage or incorrect installation.

• If damage, leakage or incorrect installation is found

Refer to Brake Assist System Diagnosis.

• Go to next step: If the inspection is OK

4. Replace the B19B Brake Booster Vacuum Sensor.

5. Verify the DTC does not set while operating the vehicle under the Conditions for Running the DTC.

• If the DTC sets

Replace the K17 Electronic Brake Control Module.

• Go to next step: If the DTC does not set

6. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Refer to Control Module References for Electronic Brake Control Module replacement, programming and setup.

DTC P050F

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Refer to Diagnostic Procedure Instructions for an overview of each diagnostic category.

DTC Descriptor

DTC P050F

Brake Booster Weak Vacuum

For symptom byte information refer to Symptom Byte List.

Circuit/System Description

The brake booster vacuum sensor measures the vacuum in the brake booster assembly. The engine control module supplies a 5 V reference and a low reference circuit to the brake booster vacuum sensor. The vacuum sensor supplies a voltage signal in relation to the pressure in the brake booster to the engine control module.

Conditions for Running the DTC

• The vehicle is in an Autostop.
• No MAP sensor DTCs set.
• No TP sensor DTCs set.

Conditions for Setting the DTC

The engine control module detected a weak vacuum in the brake booster assembly.

Action Taken When the DTC Sets

DTC P050F is a Type B DTC.

Conditions for Clearing the DTC

DTC P050F is a Type B DTC.

Reference Information

Schematic Reference

Hydraulic Brake Wiring Schematics

Connector End View Reference

Component Connector End View Index

Description and Operation

Brake Assist System Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Refer to Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON.

2. Verify that DTCs P0556, P0557, or P0558 are not set.

• If the DTC is set

Refer to DTC P0556, P0557, or P0558.

• Go to next step: If the DTC is not set

3. Has the Brake Assist System Diagnosis been performed.

• If the Brake Assist System Diagnosis has not been performed

Refer to Brake Assist System Diagnosis.

• Go to next step: If the Brake Assist System Diagnosis has been performed

4. Test or replace the B19B Brake Booster Vacuum Sensor.

5. Verify the DTC does not set while operating the vehicle under the Conditions for Running the DTC.

• If the DTC sets

Replace the K20 Engine Control Module.

• Go to next step: If the DTC does not set

6. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Refer to Power Brake Booster Vacuum Sensor Replacement (2.0L LTG) or Power Brake Booster Vacuum Sensor Replacement (3.6L LGX)
• Refer to Control Module References for K20 Engine Control Module replacement, programming and setup.

DTC P0556, P0557, or P0558

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Refer to Diagnostic Procedure Instructions for an overview of each diagnostic category.

DTC Descriptors

DTC P0556

Brake Booster Pressure Sensor Performance

DTC P0557

Brake Booster Pressure Sensor Circuit Low Voltage

DTC P0558

Brake Booster Pressure Sensor Circuit High Voltage

Diagnostic Fault Information

Circuit/System Description

The brake booster vacuum sensor monitors the pressure in the brake booster. The engine control module supplies a 5 V reference and a low reference circuit to the brake booster vacuum sensor. The vacuum sensor supplies a voltage signal in relation to the pressure in the brake booster to the engine control module.

Conditions for Running the DTC

P0556

Engine Running.

P0557 or P0558

Ignition ON/Ignition ON/Vehicle in Service Mode.

Conditions for Setting the DTC

P0556

The engine control module detects brake booster vacuum as being less than the intake manifold vacuum for more than 100 ms.

P0557

The engine control module detects less than 0.01 V on the brake booster sensor signal circuit for more than 12.5 ms.

P0558

The engine control module detects greater than 4.9 V on the brake booster sensor signal circuit for more than 12.5 ms.

Action Taken When the DTC Sets

DTCs P0556, P0557 or P0558 are Type B DTCs.

Conditions for Clearing the DTC

DTCs P0556, P0557 or P0558 are Type B DTCs.

Reference Information

Schematic Reference

Hydraulic Brake Wiring Schematics

Connector End View Reference

Component Connector End View Index

Description and Operation

Brake Booster Vacuum Assist Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

DTC Type Reference

Refer to Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Refer to Control Module References for scan tool information

Circuit/System Testing

1. Ignition OFF/Ignition OFF/Vehicle OFF and all vehicle systems OFF, disconnect the harness connector at the B19B Brake Booster Vacuum Sensor. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 10 Ω between the low reference circuit terminal 2 and ground.

• If 10 Ω or greater

1. Disconnect the harness connector at the K20 Engine Control Module.
2. Test for less than 2 Ω in the low reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K20 Engine Control Module.

• Go to next step: If less than 10 Ω

3. Ignition ON/Ignition ON/Vehicle in Service Mode.

4. Test for 4.8 - 5.2 V between the 5 V reference circuit terminal 3 and ground.

• If less than 4.8 V

1. Ignition OFF/Ignition OFF/Vehicle OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the 5 V reference circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the 5 V reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K20 Engine Control Module.

• If greater than 5.2 V

1. Ignition OFF/Ignition OFF/Vehicle OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON.
2. Test for less than 1 V between the 5 V reference circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K20 Engine Control Module.

• Go to next step: If between 4.8 - 5.2 V

5. Test for less than 1 V between the B19B Brake Booster Vacuum Sensor signal circuit terminal 1 and ground.

• If greater than 1 V

1. Ignition OFF/Ignition OFF/Vehicle OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K20 Engine Control Module.

• Go to next step: If less than 1 V

6. Ignition OFF/Ignition OFF/Vehicle OFF, disconnect the harness connector at the K20 Engine Control Module.

7. Test for infinite resistance between the B19B Brake Booster Vacuum Sensor signal circuit terminal 1 and ground.

• If less than infinite resistance

Repair the short to ground on the circuit.

• Go to next step: If infinite resistance

8. Test for less than 2 Ω in the B19B Brake Booster Vacuum Sensor signal circuit end to end.

• If 2 Ω or greater

Repair the open/high resistance in the circuit.

• Go to next step: If less than 2 Ω

9. Replace the B19B Brake Booster Vacuum Sensor.

10. Verify the DTC does not set while operating the vehicle under Conditions for Running the DTC.

• If the DTC sets

Replace the K20 Engine Control Module.

• Go to next step: If the DTC does not set

11. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Refer to Control Module References for Engine Control Module replacement, programming and setup.

Symptoms - Hydraulic Brakes

NOTE: The following steps must be completed before using the symptom tables.

1. Perform the Brake System Vehicle Road Test before using the hydraulic brake symptom tables in order to duplicate the customer's concern.

2. Review the system operation in order to familiarize yourself with the system functions. Refer to the following:

• Brake Warning System Description and Operation
• Hydraulic Brake System Description and Operation
• Brake Assist System Description and Operation

Visual/Physical Inspection

• Inspect for aftermarket devices which could affect the operation of the hydraulic brake system. Refer to Checking Aftermarket Accessories.
• Inspect the easily accessible or visible system components, for obvious damage or conditions, which could cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections.

Symptom List

Refer to the applicable diagnostic procedure in order to diagnose the symptom:

• Brake Warning Indicator Malfunction
• Brake Pulsation
• Brake System Noise
• Braking Action Uneven - Front to Rear
• Brake Pedal Excessive Travel
• Brake Pedal Excessive Effort
• Brakes Drag
• Brake System Slow Release
• Brake Fluid Loss

Brake Warning Indicator Malfunction

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Refer to Diagnostic Procedure Instructions for an overview of each diagnostic category.

Diagnostic Fault Information

Circuit/System Description

The electronic brake control module monitors the brake fluid level in the brake fluid reservoir. When the fluid within the brake fluid reservoir is below the MIN level, contacts within the brake fluid level switch closes causing the voltage within the signal circuit to drop. The electronic brake control module will detect the voltage drop and will send a serial data message to the instrument cluster commanding the brake warning indicator to illuminate.

Reference Information

Schematic Reference

Hydraulic Brake Wiring Schematics

Connector End View Reference

Component Connector End View Index

Description and Operation

Brake Warning System Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Scan Tool Reference

Refer to Control Module References for scan tool information.

Circuit/System Verification

1. Verify that the brake fluid has the proper level. The fluid level should be above minimum level.

• If low

Refer to Brake Fluid Loss.

• Go to next step: If above minimum level

2. Ignition ON.

3. Verify the scan tool Brake Fluid Level Sensor parameter. The reading should be OK.

• If the parameter is Low

Refer to Circuit/System Testing

• Go to next step: If the parameter is OK

4. Verify the brake warning indicator turns ON and OFF, when commanding the instrument cluster All Indicators ON and OFF with a scan tool.

• If the brake warning indicator does not turn ON and OFF

Replace the P16 Instrument Cluster.

• Go to next step: If the brake warning indicator turns ON and OFF

5. All OK.

Circuit/System Testing

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the B20 Brake Fluid Level Switch. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 10 Ω between the ground circuit terminal 2 and ground.

• If 10 Ω or greater

1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, repair the open/high resistance in the ground connection.

• Go to next step: If less than 10 Ω

3. Ignition ON.

4. Verify the scan tool Brake Fluid Level Sensor parameter is Low.

• If the parameter is not Low

1. Ignition OFF, disconnect the harness connector at the K17 Electronic Brake Control Module.
2. Test for infinite resistance between the signal circuit terminal 1 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the K17 Electronic Brake Control Module.

• Go to next step: If the parameter is Low

5. Install a 3 A fused jumper wire between the signal circuit terminal 1 and ground.

6. Verify the scan tool Brake Fluid Level Sensor parameter is OK.

• If the parameter is Low

1. Ignition OFF, disconnect the harness connector at the K17 Electronic Brake Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • Go to next step: If less than 1 V.
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K17 Electronic Brake Control Module.

• Go to next step: If the parameter is OK

7. Test or replace the B20 Brake Fluid Level Switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Refer to Brake Fluid Level Sensor Replacement
• Refer to Control Module References for electronic brake control module and instrument cluster replacement, programming and setup.

Brake Pulsation

WARNING: Brake fluid may irritate eyes and skin. In case of contact, take the following actions:

• Eye contact - rinse thoroughly with water.
• Skin contact - wash with soap and water.
• If ingested - consult a physician immediately.

CAUTION: Brake fluid will damage electrical connections and painted surfaces. Use shop cloths, suitable containers, and fender covers to prevent brake fluid from contacting these areas. Always re-seal and wipe off brake fluid containers to prevent spills.

CAUTION: Avoid spilling brake fluid on any of the vehicle's painted surfaces, wiring, cables or electrical connectors. Brake fluid will damage paint and electrical connections. If any fluid is spilled on the vehicle, immediately flush the area with water to minimize the potential for damage.

CAUTION: Power steering fluid, engine oil, brake fluid, or any mineral based fluids cannot be mixed. If brake seals contact power steering fluid or steering seals contact brake fluid, seal damage will result.

NOTE:

• Do not reuse the brake fluid collected during the hydraulic brake system bleeding
• Always store brake fluid in a closed container.
• Reseal brake fluid containers immediately after use.
• Do not use brake fluid left in an open container.
• Do not use brake fluid left in an improperly sealed container.
• Do not use the following fluids in the hydraulic brake system:
  • Power steering fluid
  • Automatic transmission fluid
  • DOT 5 silicone hydraulic brake fluid

For the correct brake fluid, refer to Adhesives, Fluids, Lubricants, and Sealers.

BRAKE SYSTEM NOISE

BRAKING ACTION UNEVEN - PULLS TO ONE SIDE

Test Description

The numbers below refer to the step numbers in the diagnostic table.

4

Suspension components that are not operating properly may cause a disturbance to the vehicle during application of the brake system.

5

Steering components that are not operating properly may cause a disturbance to the vehicle during application of the brake system.

BRAKING ACTION UNEVEN - FRONT TO REAR

Test Description

The number below refer to the step number in the diagnostic table:

4

Suspension components that are not operating properly may cause a disturbance to the vehicle during application of the brake system.

BRAKE PEDAL EXCESSIVE TRAVEL

BRAKE PEDAL EXCESSIVE EFFORT

BRAKES DRAG

BRAKE SYSTEM SLOW RELEASE

BRAKE FLUID LOSS

DISC BRAKE SYSTEM DIAGNOSIS

Test Description

The numbers below refer to the step numbers in the diagnostic table:

9

Lubricant leaks from non-brake system components may come in contact with and contaminate brake system components.

10

Lubricant leaks from non-brake system components may come in contact with and contaminate brake system components.

12

Disc brake rotor shields/backing plates that come in contact with disc brake rotors may cause brake system noise.

15

Disc brake rotor thickness variation that exceeds the maximum acceptable level can cause brake pulsation.

19

Disc brake rotor thickness variation that exceeds the maximum acceptable level can cause brake pulsation.

22

Disc brake rotor assembled lateral runout (LRO) that exceeds the maximum acceptable level can lead to thickness variation.

HYDRAULIC BRAKE SYSTEM DIAGNOSIS

BRAKE ASSIST SYSTEM DIAGNOSIS

Brake System Vehicle Road Test

Preliminary Inspections

1. Visually inspect easily accessible brake system components for obvious damage and/or leaks which may indicate that the vehicle should not be driven until further inspections have been completed.

2. Inspect the brake master cylinder reservoir fluid level and adjust only if necessary for brake system road testing. Brake Master Cylinder Reservoir Filling.

3. Inspect the tire inflation pressures and adjust as necessary.

4. Inspect the tire tread patterns to ensure that they are the same or very similar, especially per axle.

5. Ensure that the vehicle is not loaded unevenly prior to brake system road testing.

Road Testing Procedure

WARNING: Road test a vehicle under safe conditions and while obeying all traffic laws.

Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.

1. Start the engine and allow it to idle.

2. Check to see if the brake system warning lamp remains illuminated.

3. If the brake system warning lamp remains illuminated, DO NOT proceed to test drive the vehicle until it is diagnosed and repaired.

4. Select a smooth, dry, clean and level road or large lot that is as free of traffic and obstacles as possible for brake system low speed road testing.

5. With the transmission in PARK, lightly apply the brake pedal. Observe both the pedal feel and the pedal travel.

6. If the brake pedal apply felt spongy, or the pedal travel was excessive, DO NOT drive the vehicle until it is repaired.

7. If the brake pedal apply did not feel spongy and the pedal travel was not excessive, proceed to step 8.

8. Release and apply the brakes.

9. While continuing to apply the brakes, shift the transmission into DRIVE, release the brakes and allow the engine to idle the vehicle away from the stopped position. Observe for a slow release of the brake system.

10. With the aid of an assistant to observe the vehicle's performance from outside of the vehicle, drive the vehicle at a low speed and lightly apply the brakes while driving past the assistant. Have the assistant observe for brake system noise from the side of the vehicle closest to them, while you observe both the pedal effort and the pedal travel.

11. If the brake pedal apply effort was excessive, or the pedal travel was excessive, DO NOT continue to test drive the vehicle until it is repaired.

12. If the brake pedal apply effort was not excessive and the pedal travel was not excessive, proceed to step 13.

13. Drive the vehicle in the opposite direction, at the same low speed and lightly apply the brakes while driving past the assistant. Have the assistant observe for brake system noise from the side of the vehicle closest to him.

14. Drive the vehicle at a low speed and shift the transmission into NEUTRAL without applying the brakes. Observe for a rapid deceleration in vehicle speed, indicating possible brake drag.

15. Select a smooth, dry, clean and level road that is as free of heavy traffic as possible for brake system moderate speed road testing.

16. Drive the vehicle at a moderate speed. Observe for a pull and/or incorrect tracking of the vehicle without the brakes applied.

17. While continuing to drive the vehicle at a moderate speed, perform several light applies of the brakes. Observe the pedal effort and the pedal travel, observe for brake system noise, pulsation and/or brake drag.

18. If the brake pedal apply effort was excessive, or the pedal travel was excessive, DO NOT continue to test drive the vehicle until it is repaired.

19. If the brake pedal apply effort was not excessive and the pedal travel was not excessive, proceed to step 20.

20. While continuing to drive the vehicle at a moderate speed, perform several moderate applies of the brakes. Observe the pedal effort and the pedal travel, observe for brake system pulsation and/or uneven braking action - either side to side, or front to rear.

A small amount of vehicle front end dip is expected during a moderate apply of the brakes.

21. If the brake pedal apply effort was excessive, or the pedal travel was excessive, DO NOT continue to test drive the vehicle until it is repaired.

BRAKE PEDAL TRAVEL MEASUREMENT AND INSPECTION

Special Tools

CH-28662 Brake Pedal Effort Gauge

For equivalent regional tools, refer to Special Tools.

1. With the ignition OFF and the brakes cool, apply the brakes 3-5 times, or until the brake pedal becomes firm, in order to deplete the brake booster power reserve.

2. Install the CH-28662 gauge to the brake pedal.

3.

Measure and record the distance (1) from the brake pedal to the rim of the steering wheel; note the points of measurement.

4. Apply and maintain the brakes with 445 N (100 lb F) of force to the brake pedal, as indicated on the CH-28662 gauge.

5. While maintaining 445 N (100 lb F) of force to the brake pedal, measure and record the distance (2) from the same point on the brake pedal to the same point on the rim of the steering wheel.

6. Release the brakes and repeat steps 3 and 4 to obtain a second measurement. After obtaining a second measurement, proceed to step 7.

7. Average the first and second measurements recorded during the two applies of the brakes.

8. Subtract the initial measurement, unapplied (1), from the averaged, applied measurement (2) to obtain the brake pedal travel distance.

BRAKE SYSTEM VACUUM SOURCE TEST

Special Tools

CH-558-A Pressure Gauge

For equivalent regional tools, refer to Special Tools

NOTE:

• Engine temperature, accessory load, and elevation level will affect engine vacuum.
• Vacuum readings will decrease by approximately 2.7 kPA (0.8 in Hg) for every 305 m (1000 ft) of elevation above sea level.

Definition

If the brakes on diesel engine vehicles are operated for a long period of time, e.g. when approaching traffic lights or a traffic jam, the vacuum may be used up. The pedal travel is shortened, but will quickly return to the original pedal travel once the vacuum has been built up. Drivers often describe this phenomenon as follows: "When the brakes are operated for a long time, the brake pedal goes right to the floor" and/or as "Spongy brake pedal". On diesel vehicles, this is no cause for concern, as the pressure in the brake system is rising at this point. This can be demonstrated by connecting CH- 558-A gauge (1) to the brake calliper.

NOTE: Ignition OFF.

1. Reduce negative air pressure in brake booster.

Press brake pedal repeatedly.

2. Check brake booster.

• Press down brake pedal and maintain pressure
• Start engine

Definition

The brake system is operating correctly if the brake pedal drops further. If the brake pedal does not drop further, the vacuum system (vacuum line, non-return valve) must be checked. If no fault can be found there, replace the power brake booster. Refer to Power Brake Booster Replacement.

BRAKE SYSTEM EXTERNAL LEAK INSPECTION

WARNING: Refer to Brake Fluid Irritant Warning.

CAUTION: Refer to Brake Fluid Effects on Paint and Electrical Components Caution.

1. In order to inspect for external brake fluid leaks, first check the fluid level in the master cylinder.

While a slight brake fluid level drop can be considered a normal condition due to brake lining wear, a very low level may indicate a brake fluid leak in the hydraulic system.

If the fluid level is abnormally low, adjust the brake fluid level.

2. Start the engine and allow it to idle.

3. Apply constant, moderate foot pressure to the brake pedal.

If the brake pedal gradually falls away while under foot pressure, there may be a brake fluid leak.

4. Turn OFF the ignition.

5. Visually inspect the following brake system components for brake fluid leaks, excessive corrosion, and damage. Give particular attention to all brake pipe and flexible hose connections to ensure that there are not any slight brake fluid leaks - even though the brake pedal may feel firm and hold steady:

• Master cylinder brake pipe fittings
• All brake pipe connections
• Brake pipes
• Brake hoses and connections
• Brake calipers and/or wheel cylinders, if equipped

6. While slight dampness around the master cylinder reservoir can be considered acceptable, brake fluid leaking from any of the brake system components requires immediate attention. If any of these components exhibit signs of brake fluid leakage, repair or replace those components. After the repair or replacement, reinspect the hydraulic brake system to assure proper function.

BRAKE SYSTEM INTERNAL LEAK TEST

WARNING: Refer to Brake Fluid Irritant Warning.

CAUTION: Refer to Brake Fluid Effects on Paint and Electrical Components Caution.

1. Start the engine and allow it to idle.

2. Apply light, steady pressure to the brake pedal. Observe both the brake pedal feel and travel.

3. Release the brakes and turn OFF the ignition.

4. If the brake pedal apply felt spongy, but the brake pedal travel was not excessive, perform the following steps:

1. Inspect the brake system for external leaks. Refer to Brake System External Leak Inspection.
2. Pressure bleed the brake system in order to purge any air that may be trapped in the system.

   Refer to Hydraulic Brake System Bleeding (Pressure) or Hydraulic Brake System Bleeding (Manual).

5.

If the brake pedal apply did not feel spongy, but the brake pedal travel was excessive, perform the following steps:

1. Loosen the master cylinder-to-brake power booster mounting nuts.
2. Carefully pull the master cylinder away from the brake power booster just enough to inspect the mounting surface of the master cylinder.
3. Inspect the master cylinder mounting surface at the primary piston (2) for brake fluid leaks.

6. If the master cylinder exhibits any leakage around the primary piston (2), then the primary piston primary seal (4) and/or secondary seal (3) is leaking and the master cylinder requires overhaul or replacement.

7. If the master cylinder primary piston (2) does not exhibit any leakage, pressure bleed the brake system. Refer to Hydraulic Brake System Bleeding (Pressure) or Hydraulic Brake System Bleeding (Manual).

8. If the brake pedal apply did not feel spongy, and the brake pedal travel was initially steady and not excessive, but then gradually fell, then the master cylinder requires overhaul or replacement due to an internal leak past the secondary piston (1) from the secondary piston primary seal (6) or secondary seal (5).

9. If the brake pedal apply did not feel spongy, and the brake pedal travel was initially steady and not excessive, then fell slightly, then became steady again, then the brake pressure modulator valve (BPMV) may be leaking internally, and may require replacement.

Hydraulic Brake Component Operation Visual Inspection

1.

WARNING: Refer to Brake Fluid Irritant Warning. CAUTION: Refer to Brake Fluid Effects on Paint and Electrical Components Caution.

With the tire and wheel assemblies removed and the brake rotors retained by wheel lug nuts, visually inspect the caliper piston dust boot (2) sealing area to ensure that there are no brake fluid leaks.

2. If any evidence of a brake fluid leak is present, the brake caliper requires overhaul or replacement.

3. While the brake system is at rest (4), observe the position of the caliper piston (1) in relation to the caliper housing.

4. Have an assistant apply and release the brake pedal several times while you observe the operation of the hydraulic brake caliper.

1. Observe the caliper piston (1) for unrestricted and even movement during each apply of the brake system (5).
2. Observe the caliper piston (1) for an unrestricted and even return motion during each release of the brake system (6).

5. If the caliper piston (1) did not exhibit unrestricted and even movement during brake system apply and/or release, the piston square seal (3) may be worn or damaged and the caliper may require overhaul or replacement.

BRAKE PIPE AND HOSE INSPECTION

WARNING: Refer to Brake Fluid Irritant Warning.

CAUTION: Refer to Brake Fluid Effects on Paint and Electrical Components Caution.

1. Visually inspect all of the brake pipes for the following conditions:

• Kinks, improper routing, missing or damaged retainers
• Leaking fittings, excessive corrosion

2. If any of the brake pipes exhibited any of the conditions listed, then the identified pipe, or pipes, require replacement.

3. Ensure that the vehicle axles are properly supported at ride height in order to maintain the proper relationship of the flexible brake hoses to the chassis.

4.

Visually inspect all of the flexible brake hoses for the following conditions:

• Kinks (1), improper routing, twists, chafing, missing or damaged retainers
• Leaking connections, cracking, dry-rot, blisters, bulges

5. If any of the flexible brake hoses exhibited any of the conditions listed, then the identified flexible brake hose, or hoses require replacement.

6. Squeeze the flexible brake hoses with firm finger pressure to check for soft spots (2), indicating an internal restriction. Check the entire length of each flexible brake hose.

7. If any of the flexible brake hoses were found to have soft spots (2), then the identified flexible brake hose, or hoses require replacement.

BRAKE PEDAL PUSHROD INSPECTION

1.

Disconnect the brake pedal pushrod (2) from the brake pedal.

2. Reposition the pedal pushrod boot (1) toward the front of the vehicle to expose as much of the pedal pushrod (2) as possible.

3. Inspect the brake pedal pushrod (2) for straightness.

4. If the brake pedal pushrod (2) is not straight, then the pushrod requires replacement.

5. Return the pedal pushrod boot (1) to its original position on the pedal pushrod (2).

6. Connect the brake pedal pushrod (2) to the brake pedal.

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