B12C0

B12C0-15-BRAKE FLUID LEVEL SWITCH - CIRCUIT SHORT TO BATTERY OR OPEN

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The Body Control Module (BCM) provides a reference voltage on the brake fluid level signal circuit through a pull-up resistor. The Brake Fluid Level Switch switches the brake fluid level signal circuit to ground when the fluid level is low. A diagnostic resistor internal to the switch is placed in parallel with the switch.

- When Monitored:
With the ignition on.

- Set Condition:
When the BCM detects that the parallel resistor is not detected in the circuit and the switch is not closed.





1. CHECK FOR ACTIVE DIAGNOSTIC TROUBLE CODE (DTC)
1. Turn the ignition on.
2. With the scan tool, clear all DTCs.
3. With the scan tool, read DTCs.

Does the scan tool display this DTC as active?

Yes

- Go To 2

No

- Test complete, the condition or conditions that originally set this DTC are not present at this time. Using the wiring diagrams as a guide, check all related splices and connectors for signs of water intrusion, corrosion, pushed out or bent terminals, and correct pin tension.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

2. CHECK THE (B20) BRAKE FLUID LEVEL SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE
1. Turn the ignition off.
2. Disconnect the Brake Fluid Level Switch harness connector.
3. Disconnect the BCM C1 harness connector.
4. Turn the ignition on.
5. Measure the voltage between ground and the (B20) Brake Fluid Level Signal circuit.

Is there any voltage present?

Yes

- Repair the short to voltage in the (B20) Brake Fluid Level Signal circuit.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

No

- Go To 3

3. CHECK THE (B20) BRAKE FLUID LEVEL SIGNAL CIRCUIT FOR AN OPEN
1. Turn the ignition off.
2. Measure the resistance of the (B20) Brake Fluid Level Signal circuit between the Brake Fluid Level Switch harness connector and the BCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 4

No

- Repair the open in the (B20) Brake Fluid Level Signal circuit.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

4. CHECK THE (Z910) GROUND CIRCUIT FOR AN OPEN
1. Using a 12-volt test light connected to 12-volts, check the (Z910) Ground circuit at the Brake Fluid Level Switch harness connector.

Does the test light illuminate brightly?

Yes

- Go To 5

No

- Repair the open in the (Z910) Ground circuit.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

5. CHECK THE BCM FOR CORRECT OPERATION
1. Turn the ignition off.
2. Reconnect the BCM C1 harness connector.
3. Connect a jumper wire between the (B20) Brake Fluid Level Signal circuit and the (Z910) Ground circuit at the Brake Fluid Level Switch harness connector.
4. Turn the ignition on.
5. With the scan tool, read the Brake Fluid Level.

Does the Brake Fluid Level display Low Level?

Yes

- Replace the Brake Fluid Level Switch. Brake Fluid Level Switch - Removal.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

No

- Replace the BCM. Body Control Module - Removal.
- Perform the BODY VERIFICATION TEST. Body Verification Test.