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 Instructionsprovides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The instrument cluster turns ON the brake warning indicator for 5 s after ignition ON. The body control module (BCM) monitors the parking brake switch and will request the instrument cluster via serial data to turn the brake warning indicator ON when the parking brake is applied. When the electronic brake control module (EBCM) detects a fault, it sends a serial data message to the instrument cluster commanding the indicator ON.
Reference Information
Schematic Reference
Hydraulic Brake Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Sunshade - Left (D6I)
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 Control Module Referencesfor scan tool information
Circuit/System Verification
1. Verify the park brake is released and the brake fluid is at or above the proper 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 B80 Park Brake Switch.
2. Ignition ON, verify the scan tool BCM Park Brake Status parameter is Inactive.
• If not the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the K9 Body Control Module.
3. Install a 3 A fused jumper wire between the signal circuit terminal 1 and ground.
4. Verify the scan tool BCM Park Brake Status parameter is Active.
• If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.
5. If all circuits test normal, test or replace the B80 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 ohm between the ground circuit terminal 2 and ground.
• If greater than the specified value, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool EBCM Brake Fluid Level Sensor parameter is Low.
• If not the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the K17 Electronic Brake Control Module.
4. Install a 3 A fused jumper wire between the signal circuit terminal 1 and ground.
5. Ignition OFF, ignition ON, verify the scan tool Brake Fluid Level parameter is OK.
• If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K17 Electronic Brake Control Module.
6. 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 B80 Park Brake Switch.
2. Test for infinite resistance between the signal terminal 1 and ground with the park brake released.
• If less than the specified value, replace the B80 Park Brake Switch.
3. Test for less than 5 ohm between the signal terminal 1 and ground with the park brake applied.
• If greater than the specified value, replace the B80 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 ohm between the ground circuit terminal 2 and the signal circuit terminal 1.
• If less than the specified value, replace the B20 Brake Fluid Level Switch.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Brake Fluid Level Indicator Switch Replacement Service and Repair
* Parking Brake Indicator Switch Replacement Service and Repair
* Control Module References Control Module Referencesfor BCM, instrument panel cluster, and EBCM replacement, programming and setup