Normal Operation

The ABS module uses an internal solid state switch to operate the ABS pump motor. When the engine speed is above 700 rpm or the vehicle speed is at approximately 7 km/h (4 mph), the ABS module will test the ABS pump motor by activating it for 30 milliseconds. While the pump motor is being activated, the ABS module monitors the voltage drop across the ABS pump motor solid state switch and the amount of current the ABS pump motor draws through the solid state switch. If the voltage drop is too high or if the ABS pump motor is drawing too much current, the ABS module will set a DTC. After 30 milliseconds have passed, the ABS module will stop applying voltage to the pump motor and observe the voltage that the spinning ABS pump motor is generating. The voltage generated by the motor indicates how fast the motor is spinning. A voltage that is too low indicates that the motor is not spinning freely and a DTC will set.

Fused battery voltage from Battery Junction Box (BJB) fuse 8 (50A) along circuit SBB08 (VT/RD) is used by the ABS module to power the ABS pump motor. The ABS module provides ground for the ABS pump motor from GD121 (BK/YE). Insufficient power or ground along from these circuits will cause multiple DTCs to set.

• DTC C0020:13 (ABS Pump Motor Control: Circuit Open) - If the voltage supplied to the ABS module is less than 10 volts, if there is an open or high resistance on the ABS pump motor circuit between the ABS module and the Hydraulic Control Unit (HCU), or if the ABS module is faulted internally, this DTC will set.
• DTC C0020:71 (ABS Pump Motor Control: Circuit Actuator Stuck) - If the ABS module detects that the ABS pump motor is not rotating, when it is commanded to run, this DTC will set.

  This pinpoint test is intended to diagnose the following: 

• Fuse(s)
• Wiring, terminals or connectors
• HCU
• ABS module