C121E

C121E - Brake Pressure Sensor Comparative Performance

For a complete wiring diagram, refer to.

• 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.






Test Step 1 - Test for DTC C121E - Brake Pressure Sensor Comparative Performance

• 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 the DTCs.

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

• With the scan tool, erase the DTCs.

• Start the engine.

• Slowly press and release the brake pedal.

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

Does the scan tool display C121E - Brake Pressure Sensor Comparative Performance?

Yes

• Go to Test Step 2 => [ Test Step 2 - HCU/ECU Isolation ]

No

• Perform the ABS Intermittent Condition Test. Refer to=> Non-DTC Based Diagnostics. ABS Intermittent Condition Test

Test Step 2 - HCU/ECU Isolation

• Turn the ignition OFF.

• Separate the ECU from the HCU.

• Turn the ignition ON.

• With the scan tool, monitor the brake pressure.

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

Yes

• Replace the HCU.

• Perform ABS Verification Test. Refer to => Non-DTC
Based Diagnostics. ABS Verification Test

No

• Replace the ECU. Perform ABS Verification Test. Refer to => Non-DTC Based Diagnostics. ABS Verification Test