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 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.
Reference Information
Schematic Reference
Hydraulic Brake Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Hybrid/EV Battery Pack X1
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 Relearningfor scan tool information
Circuit/System Verification
1. Verify 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 P16 Instrument Cluster.
3. Vehicle in Service Mode, observe the scan tool Brake Fluid Level Sensor parameter. The reading should be OK.
Circuit/System Testing
1. Vehicle 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. Vehicle in Service Mode, 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.
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.
5. If all circuits test normal, test or replace the B20 Brake Fluid Level Switch.
Component Testing
Static Test
1. Vehicle OFF, disconnect the harness connector at the B20 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 B20 Brake Fluid Level Switch.
3. Test for less than 5 ohm between the signal terminal A and ground terminal B with the switch in the closed position.
• If greater than the specified range, replace the B20 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
* Control Module References Programming and Relearningfor instrument panel cluster, and control module replacement, programming and setup