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.

Slowly 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
1. Go to 2).
No
1. Refer to the INTERMITTENT CONDITION diagnostic procedure.
2. Refer to ABS INTERMITTENT CONDITION .
2) 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 218 bar (3162 psi)?

Yes
1. Replace the HCU in accordance with the SERVICE INFORMATION.
2. Perform ABS VERIFICATION TEST .
No
1. Replace the ECU in accordance with the SERVICE INFORMATION.
2. Perform ABS VERIFICATION TEST .