C0121

DTC C0121

Circuit Description

An internal solenoid valve relay in the electronic brake control module (EBCM) supplies battery positive voltage to all solenoid valves. This voltage is referred to as system voltage. The EBCM activates the solenoid valve relay when the ignition is turned ON. Once the solenoid valve relay has been activated, The EBCM supplies ground to actuate individual solenoid valves.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C0121 Valve Relay Circuit

Conditions for Running the DTC

^ The ignition is ON.
^ Ignition voltage is greater than 8 volts.

Conditions for Setting the DTC

One of the following conditions exists for 0.23 seconds:

^ The EBCM commands the solenoid valve relay on and battery voltage is not present at the solenoid valves.
^ The EBCM commands the solenoid valve relay off and battery voltage is present at the solenoid valves.

Action Taken When the DTC Sets

^ The EBCM disables the ABS system.
^ The ABS indicator turns ON.
^ DRP function is degraded.

Conditions for Clearing the DTC

^ The condition for the DTC is no longer present and the DTC is cleared with a scan tool.
^ The electronic brake control module (EBCM) automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

Diagnostic Aids

The solenoid valve relay is integral to the EBCM. The relay is not serviceable.

Test Description

The number below refers to the step number on the diagnostic table.
2. This step determines whether the DTC is current.

Step 1 - Step 4: