Brake Warning Indicator Malfunction
Brake Warning Indicator Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The brake fluid level switch monitors the level of brake fluid in the master cylinder. When the electronic brake control module (EBCM) sees the brake fluid level switch input grounded, it sends a serial data message to the instrument panel cluster to turn ON the Red Brake Warning indicator.
The BCM sees the park brake switch input grounded and sends a serial data message to the instrument panel cluster requesting illumination of the Red Brake Warning indicator.
Reference Information
Schematic Reference
Hydraulic Brake Schematics Electrical Diagrams
Connector End View Reference
Component Connector End Views Sunshade - Left Front
Description and Operation
Brake Warning System Description and Operation Brake Warning System
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Programming and Relearning for scan tool information
Circuit/System Verification
1. Verify the park brake is released and the brake fluid is at or above the minimum level.
• If low, refer to Brake Fluid Loss Brake Fluid Loss.
2. Command the instrument panel cluster lamp test with a scan tool, the warning indicator should turn ON.
• If the red brake warning indicator does not illuminate, replace the instrument panel cluster.
3. Ignition ON, observe the scan tool BCM Park Brake Switch parameter while applying and releasing the park brake. The parameter should cycle between Applied and Released.
• If the parameter does not cycle between the specified values, refer to Park Brake Switch Malfunction.
4. Observe the scan tool EBCM Brake Fluid Level parameter. The reading should be OK.
• If not the specified value, refer to Brake Fluid Level Switch Malfunction.
Circuit/System Testing
Park Brake Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the park brake switch.
2. Ignition ON, verify the scan tool BCM Park Brake Switch parameter is Released.
• If not the specified value, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the BCM.
3. Install a 3 A fused jumper wire between the signal circuit terminal A and ground. Verify the scan tool BCM Park Brake Switch parameter is Applied.
• If not the specified value, test the signal circuit for a short to voltage or an open/high resistance.
4. If all circuits test normal, test or replace the park brake switch.
Brake Fluid Level Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the B20 brake fluid level switch.
2. Test for less than 5 ohms between the ground circuit terminal B and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Brake Fluid Level Sensor parameter is OK.
• If not the specified value, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the K17 electronic brake control module (EBCM).
Note:
The parameter may take up to 60 seconds to switch from OK to Low.
4. Install a 3 A fused jumper wire between the signal circuit terminal A and ground circuit terminal B. Verify the scan tool Brake Fluid Level Sensor parameter is Low.
• If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the K17 electronic brake control module (EBCM).
5. If all circuits test normal, test or replace the B20 brake fluid level switch.
Component Testing
Park Brake Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the park brake switch.
2. Test for infinite resistance between the signal terminal A and ground with the park brake released.
• If less than the specified value, replace the park brake switch.
3. Test for less than 1 ohms between the signal terminal A and ground with the park brake applied.
• If greater than the specified range, replace the park brake switch.
Brake Fluid Level Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the brake fluid level switch.
2. Test for infinite resistance between the ground terminal B and the signal terminal A with the switch in the open position.
• If less than the specified value, replace the brake fluid level switch.
3. Test for less than 5 ohms between the signal terminal A and ground terminal B with the switch in the closed position.
• If greater than the specified range, replace the brake fluid level switch.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Master Cylinder Reservoir Replacement Service and Repair
* Parking Brake Indicator Switch Replacement Service and Repair
* Control Module References Programming and Relearning for BCM, instrument panel cluster, and EBCM replacement, setup, and programming