A042

DTC A042 Rear ESB Will Not Hold Motor:

DTC A0B Will Not Hold Motor:

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

Failure Condition:
DTC A042 can be set during initialization. If the EBCM detects that the ESB could not hold the piston in the home position, a malfunction exists. DTC AO86 is always set with DTC AO42.

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. DTCs AO42 and AO86 are stored, ABS is disabled and the "ABS" and "BRAKE" indicators are turned on. The "ABS" indicator will flash if the EBCM cannot illuminate the "BRAKE" indicator.

Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This step checks the rear ESB. A broken or defective ESB would result in the rear piston being backdriven by hydraulic pressure and pedal movement would result.
2. This test checks for high resistance in the rear motor high circuit.
3. This test checks for high resistance in the rear motor low circuit.
4. This test checks for high resistance in the rear motor.
5. This test determines if the fault is due to poor terminal contact or corrosion.
6. This test determines if the fault is due to a faulty 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 feature of the TECH 1.

The static modulator test function of the TECH 1 may be used to locate an intermittent malfunction associated with the ESB.