Brake Warning Indicator Malfunction (With Antilock Brake System)
Brake Warning Indicator Malfunction (With Antilock Brake System)
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 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 (Connector End Views By Name)
Description and Operation
Hydraulic Brake System Description and Operation (Hydraulic Brake 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. Inspect for proper brake fluid level. The fluid level should be above minimum level.
• If low, refer to Brake Fluid Loss (Brake Fluid Loss).
2. Ignition ON, with a scan tool command the instrument cluster All Indicators test ON and OFF. Verify the brake warning indicator turns ON and OFF.
• If the brake warning indicator does not turn ON and OFF, replace the P16 Instrument Cluster.
3. Observe the scan tool BCM Park Brake Switch parameter while applying and releasing the parking brake. Verify the reading changes between Active and Inactive.
• If the parameter does not change between the specified values, refer to Park Brake Switch Malfunction.
4. Apply the parking brake. Verify the brake warning indicator turns ON.
• If the brake warning indicator does not turn ON, replace the K9 Body Control Module.
5. Release the parking brake. Verify the brake warning indicator turns OFF.
• If the brake warning indicator does not turn OFF, refer to Brake Fluid Level Switch Malfunction.
Circuit/System Testing
Note: Circuit/System Verification must be performed before Circuit/System Testing.
Park Brake Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the B80 Park Brake Switch.
2. Inspect the B80 Park Brake Switch for physical damage and correct installation.
• If physical damage or incorrect installation is diagnosed, repair or replace the B80 Park Brake Switch.
3. Ignition ON, verify the scan tool BCM Park Brake Switch 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.
4. Install a 3 A fused jumper wire between the signal circuit terminal 1 and ground.
5. Verify the scan tool BCM Park Brake Switch 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.
6. 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 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 for a short to ground. If the circuit tests normal, replace the K17 electronic brake control module (EBCM).
4. Install a 3 A fused jumper wire between the signal circuit terminal A and ground.
5. Verify the scan tool Brake Fluid Level Sensor parameter is LOW.
• 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 (EBCM).
6. If all circuits test normal, test or replace the B20 brake fluid level switch.
Component Testing
Park Brake Switch Test
1. Ignition OFF, disconnect the harness connector at the B80 Park Brake Switch.
2. Test for infinite resistance between the signal circuit terminal 1 and the ground circuit terminal 2 with the parking brake released.
• If less than the specified value, replace the B80 Park Brake Switch.
3. Test for less than 5 ohm between the signal circuit terminal 1 and the ground circuit terminal 2 with the park brake applied.
• If greater than the specified value, replace the B80 Park Brake Switch.
Brake Fluid Level Switch Test
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 diagnostic procedure.
* Brake Fluid Level Indicator Switch Replacement (Service and Repair)
* Parking Brake Indicator Switch Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for module replacement, setup and programming