C121D-BRAKE PRESSURE SENSOR CIRCUIT

For a complete wiring diagram Refer to Section 8W.

When Monitored:
With the ignition on.
Set Condition:
When the Anti-Lock Brake Module indicates that the Brake Pressure Sensor Signal is out of range.

Possible Causes

AIR IN BRAKE SYSTEM/WORN MECHANICAL COMPONENTS

ECU INTERNAL FAILURE

HCU INTERNAL FAILURE

Diagnostic Test

1. CHECK FOR A DTC C121D-BRAKE PRESSURE SENSOR CIRCUIT

NOTE: This DTC must be active for the results of this test to be valid.

Turn the ignition on.
With the scan tool, read and record DTCs.
With the scan tool, read and record Freeze Frame information.
With the scan tool, erase DTCs.
Start the engine.
Depress and release the brake pedal.
With the scan tool, read and record DTCs.

Does the scan tool display: C121D-BRAKE PRESSURE SENSOR CIRCUIT?

Yes

Go To 2

No

Refer to the INTERMITTENT CONDITION diagnostic procedure.
Refer to the ABS-INTERMITTENT CONDITION TEST. (Refer to 5 - BRAKES - DIAGNOSIS AND TESTING)

2. RECHECK FOR A DTC C121D-BRAKE PRESSURE SENSOR CIRCUIT

Turn the ignition on.
With the scan tool, read and record DTCs.
With the scan tool, read and record Freeze Frame information.
With the scan tool, erase DTCs.
Start the engine.
Depress and release the brake pedal.
With the scan tool, read and record DTCs.

Does the scan tool display: C121D-BRAKE PRESSURE SENSOR CIRCUIT?

Yes

Go To 3
Perform ABS VERIFICATION TEST. (Refer to 5 - BRAKES - STANDARD PROCEDURE).

No

Test complete

3. HCU/ECU ISOLATION

Turn the ignition off.
Separate the ECU from the HCU.
With the scan tool, monitor brake pressure.

Does the scan tool display brake pressure above 200 psi?

Yes

Replace the HCU in accordance with the Service Information.

Perform ABS VERIFICATION TEST. (Refer to 5 - BRAKES - STANDARD PROCEDURE).

No

Replace the ECU in accordance with the Service Information.
Perform ABS VERIFICATION TEST. (Refer to 5 - BRAKES - STANDARD PROCEDURE).