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 (IPC) to turn ON the Red Brake Warning indicator. The body control module (BCM) sees the park brake switch input grounded, it sends a serial data message to the IPC requesting illumination of the Red Brake Warning indicator.

Schematic Reference

Hydraulic Brake Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Brake Warning System Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

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.

2. Command the IPC lamp test with a scan tool, the warning indicator should turn ON.

⇒	If the red brake warning indicator does not illuminate, replace the IPC.

3. Ignition ON, observe the scan tool BCM Park Brake Switch parameter while applying and releasing the park brake. The parameter should cycle between Set 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 Switch parameter. The reading should be OK.

⇒	If not the specified value, refer to Brake Fluid Level Switch Malfunction.

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 3A fused jumper wire between the signal circuit terminal A and ground. Verify the scan tool BCM Park Brake Switch parameter is Set.

⇒	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 brake fluid level switch.
2. Test for less than 1 ohm between the ground circuit terminal A and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the scan tool EBCM Brake Fluid Level Switch parameter is OK.

⇒	If not the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the EBCM.

4. Install a 3A fused jumper wire between the signal circuit terminal B and ground. Verify the scan tool EBCM Brake Fluid Level Switch 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 EBCM.

5. If all circuits test normal, test or replace the brake fluid level switch.

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 ohm 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 A and the signal terminal B.

⇒	If less than the specified value, replace the brake fluid level switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.