C0121

DTC C0121





Circuit Description
The electronic brake control module (EBCM) energizes the solenoid valve relay when the ignition switch is ON. The solenoid valve relay applies voltage to the solenoid valve coils. The solenoid valve relay remains energized until the ignition switch is turned OFF, or the ABS/TCS is disabled.

DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0121 Valve Relay Circuit

Conditions for Running the DTC
DTC C0121 can be set anytime the ignition switch is in the ON position.

Conditions for Setting the DTC
The EBCM detects a short, low voltage, invalid signal, or incorrect valve relay operation.

Action Taken When the DTC Sets
^ The ABS and traction control system are disabled.
^ The ABS, TRAC OFF and BRAKE warning indicators turn ON.

Conditions for Clearing the DTC
The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

Diagnostic Aids
Thoroughly inspect the wiring and the connectors. An incomplete inspection of the wiring and the connectors may result in a misdiagnosis, causing a part replacement with the reappearance of the malfunction.
The following are possible causes of the malfunction:
^ An open, or high resistance in the EBCM ground circuit
^ An open, high resistance or short to ground in the EBCM battery supply voltage circuits
^ An internal EBCM malfunction

If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
5. This step tests the EBCM ground circuit for an open, or high resistance.
6. This step tests the battery supply voltage circuits of the EBCM for an open, high resistance or short to ground.