A042

Diagnostic Chart:

Wiring Diagram:

Circuit Description:
This DTC is designed to detect a slipping rear axle ESB. During initialization and braking, the rear motor is re-homed. If the ESB slips, the motor/piston will move. During the next key "ON" initialization, a re-home of the motor verifies the motor/piston remained at the home position. If motor movement is detected, the ESB must be slipping.

Failure Condition:

DTC A042 cannot be set during initialization. If the EBCM detects that the ESB could not hold the piston in the home position, a malfunction exists. DTC A086 is always set with DTC A042.

Action Taken:
If an ESB cannot hold a piston in the home position, the piston may be backdriven when the brake pedal is applied, causing the brake pedal to drop. A malfunction DTC is stored, ABS is disabled, and the "ABS INOP" lamp and the red "BRAKE" warning lamp are turned "ON."

Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This step checks the rear axle ESB. A broken or defective ESB would result in the rear axle pistons being backdriven by hydraulic pressure and wheel movement would result.
2. This step insures that the proper motor circuits are located in the proper connector cavities.
3. This step checks for high resistance in the motor "HIGH" circuitry.
4. This step checks for high resistance in the motor "LOW" circuitry.
5. This step checks for proper resistance of the motor windings.
6. This step checks for poor terminal contact or corrosion in the connectors.
7. This steps checks for a malfunctioning EBCM.

Diagnostic Aids:
An "Intermittent" malfunction in this DTC may result from a mechanical part of the system that sticks, binds, or slips.

The frequency of the malfunction can be checked by using the enhanced diagnostic function of the Tech 1, as described in "Tech 1 Diagnostics."

The static modulator test function of the Tech 1 or T-100 may be used to locate an intermittent malfunction associated with the ESB.