Antilock Braking System (ABS)

DTC 66 Rear Axle Motor Circuit Shorted To Battery Or Motor Shorted:

CIRCUIT DESCRIPTION
This DTC identifies a motor circuit that is shorted to battery or a motor that has low or zero resistance. This malfunction will not allow the motor to be controlled at the commanded current rate or will cause the motor to turn in the opposite direction or not turn at all.

FAILURE CONDITION
DTC A066 can be set anytime. If the EBCM detects an out of range voltage in either of the rear axle motor circuits indicating a circuit shorted to battery or a motor shorted, a malfunction exists.

ACTION TAKEN
A malfunction DTC is stored, ABS is disabled and the ABS indicator lamp is turned "ON."

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This step checks for a short to voltage in the motor "high" circuitry.
2. This step checks for a short to voltage in the motor "low" circuitry.
3. This step checks for a motor that is internally shorted.
4. This step is used to release the tension of the motor pack prior to removal.

DIAGNOSTIC AIDS
Using Tech 1, select manual control function, and exercise motor movement of affected channel in both directions while applying light pressure on the brake pedal.

If erratic or "jumpy" brake pedal movement is detected while performing an "apply" or "release" function of the motor, an intermittent malfunction may be indicated.

An "Intermittent" malfunction may be caused by a poor connection, rubbed through wire insulation, or a wire that is broken inside the insulation.

If the malfunction is not current, wiggle the wires of the affected channel and check if the DTC resets. This will help to pinpoint an intermittent malfunction in the motor circuitry or connections.

The frequency of the malfunction can be checked by using the enhanced diagnostic function of the Tech 1.

If DTC A042 sets as current DTC and A066 is infrequent history DTC, see DTC A042 diagnostics.

Any circuitry, that is suspected as causing the intermittent complaint, should be thoroughly checked for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wiring connections or physical damage to the wiring harness.