Circuit Description

When the antilock brake system (ABS) is active, the valve relay provides voltage to actuate the solenoid valves. The valves do not use this voltage unless the ABS control module provides the ground for each solenoid coil.

DTC C0121 will set if the valve relay voltage is low or if the relay supply line is at 12 volts when the ABS control module is not requesting it. This diagnostic trouble code (DTC) will also set if the ABS control module detects 3 or more solenoid valve circuits are open or shorted during the self-test.

This procedure checks whether there is a poor ground connection for the electronic brake control module (EBCM).