C1242

CIRCUIT DESCRIPTION
Diagnostic Trouble Code (DTC) C1242 detects a slipping rear axle ESB. During initialization and braking, the rear motor is rehomed. If the ESB slips, the motor/piston will move. During the next keg, to RUN initialization, a rehome of the motor verifies the motor/piston remained at the home position. If motor movement is detected, the ESB must be slipping.
If an ESB cannot hold a piston in the home position, the piston may be driven back when the brake pedal is applied. Then the brake pedal will drop.
DTC C1286 is always set with this DTC.

CONDITIONS FOR SETTING THE DTC
Diagnostic Trouble Code (DTC) C1242 can set during initialization at the following speeds:
^ 0 km/h (0 mph) when the brake is OFF
^ 5 km/h (3 mph) when the brake is ON A malfunction exists if the Electronic Brake Control Module (EBCM) detects that the ESB could not hold the piston in the home position. DTC C1286 always sets with DTC C1242.

ACTION TAKEN WHEN THE DTC SETS
^ A malfunction Diagnostic Trouble Code (DTC) stores.
^ The ABS disables.
^ The ABS warning indicator turns ON.

CONDITIONS FOR CLEARING THE DTC
^ The condition responsible for setting the Diagnostic Trouble Code (DTC) no longer exists and the Scan Tool Clear DTCs function is used.
^ 100 drive cycles pass with no DTCs detected. A drive cycle consists of starting the vehicle, driving the vehicle over 16 km/h (10 mph), stopping and then turning the ignition OFF.

DIAGNOSTIC AIDS
The following conditions may cause an intermittent malfunction if the conditions exist in a mechanical part of the system:
^ Sticking
^ Binding
^ Slipping

Use the enhanced diagnostic function of the Scan Tool in order to measure the frequency of the malfunction.
Use the hydraulic control modulator test function of the Scan Tool in order to locate an intermittent malfunction associated with the ESB.
Clear the Diagnostic Trouble Codes (DTCs) after completing the diagnosis. Test drive the vehicle for three drive cycles in order to verify that the DTC does not reset. Use the following procedure in order to complete one drive cycle:
1. Start the vehicle.
2. Drive the vehicle over 16 km/h (10 mph).
3. Stop the vehicle.
4. Turn the ignition to the OFF position.

TEST DESCRIPTION
2. This test ensures that the motor circuits are in the proper connector cavities.
3. This test checks the operation of the rear ESB.
4. This test checks for high resistance in the rear motor high circuit.
5. This test checks for high resistance in the rear motor low circuit.
6. This test checks for excessive resistance in the rear motor.
8. This test determines if the malfunction is caused by the Electronic Brake Control Module (EBCM).

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Part 2 Of 2:

DTC C1242 REAR ESB DOES NOT HOLD MOTOR