67 Pump Motor Circuit Open

NAME OF CODE:
67 Pump Motor Circuit Open


SET CONDITION:
The following criteria must be met for this trouble code to be detected:

1. Ignition turned on for at least 3.4 seconds.
2. ABS power relay command given for at least 15 ms.
3. CAB pump/motor command never given during the current ABS power relay command.
4. Low feedback voltage from the low side of motor.
5. Criteria 1-4 satisfied for 30 consecutive controller checks spaced 5 ms apart.


THEORY OF OPERATION:
Whenever a power relay command is given and a motor command is not given, so that the motor should not be turning and generating a back-EMF, the motor winding can be considered a low impedance pull-up resistor. Consequently, the feedback voltage from the low side of the motor should be high. If it is not, and the problem persists long enough to rule out noise input, a Pump Motor Circuit Open code is set.


POSSIBLE CAUSES:
- Anything that keeps motor feedback voltage low when the power relay is supposed to be closed and the motor armature is supposed to be stationary
- Open motor winding
- Shorted CAB motor driver output
- Open Circuit in series with the motor (excluding an open relay)
- Short to ground in the motor feedback to the CAB microprocessor