DTC C0121: Valve Relay Circuit Malfunction: Notes

Fig 1: C0121 - Valve Relay Circuit Malfunction Schematic

Courtesy of GENERAL MOTORS CORP.

The ABS control module uses a relay to control valve solenoids. When ignition is in the Run position, the module energizes the relay winding to switch battery voltage that supplies the solenoids. The module will disable the relay when ignition is Off, or a fault is detected.