C121E-BRAKE PRESSURE SENSOR COMPARATIVE PERFORMANCE

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

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
ECU INTERNAL FAILURE
HCU INTERNAL FAILURE

1. CHECK FOR A DTC C121E-BRAKE PRESSURE SENSOR COMPARATIVE PERFORMANCE

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

1.	Turn the ignition on.

2.	With the scan tool, read and record the DTCs.

3.	With the scan tool, read and record the Environmental Data to help identify the conditions in which the DTC was set.

4.	With the scan tool, erase the DTCs.

5.	Start the engine.

6.	Slowly press and release the brake pedal.

7.	With the scan tool, read and record the DTCs.

Does the scan tool display: C121E-BRAKE PRESSURE SENSOR COMPARATIVE PERFORMANCE?

Yes

2. HCU/ECU ISOLATION

1.	Turn the ignition off.

2.	Separate the ECU from the HCU.

3.	Turn the ignition on.

4.	With the scan tool, monitor the brake pressure.

Does the scan tool display brake pressure above 218 bar (3162 psi)?

Yes

Replace the HCU in accordance with the Service Information.
Perform the ABS VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Antilock Brake (ABS) - Standard Procedure).

Replace the ECU in accordance with the Service Information.
Perform the ABS VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Antilock Brake (ABS) - Standard Procedure).