Circuit Description
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 key 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.
Conditions for Setting the DTC
DTC C1242 can set during initialization at the following speeds:
| • | 0 km (0 mph) when the brake is off |
| • | 5 km (3 mph) when the brake is on |
A malfunction exists if the 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 DTC stores. |
| • | The ABS disables. |
| • | The amber ABS warning indicator turn on. |
| • | The red BRAKE warning indicator turns on. |
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTCs function is used. |
| • | 100 drive cycles pass with no DTC(s) detected. |
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. Refer to the Scan Tool manual for the procedure.
Use the hydraulic control modulator test function of the Scan Tool in order to locate an intermittent malfunction associated with the ESB.
Clear the 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:
- Start the vehicle.
- Drive the vehicle over 16 km/h (10 mph).
- Stop the vehicle.
- Turn the ignition to the OFF position.
Important: Zero the J 39200 test leads before making any resistance measurements. Refer to the J 39200 user's manual.
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Diagnostic System Check performed? | -- | Go to Diagnostic System Check | |||||||||
2 | Inspect the following connectors for the correct wire color/connector cavity combinations:
Are the correct wires located in the correct connector cavities? | -- | ||||||||||
3 |
Do not start the engine. Does the brake pedal fall? | -- | ||||||||||
4 |
Is the resistance within the specified range? | 0-1.5 ohms | ||||||||||
5 | Use the J 39200 in order to measure the resistance between the 6-way ABS brake motor pack harness connector terminal C and the 8-way EBCM harness connector C2 terminal E. Is the resistance within the specified range? | 0-1.5 ohms | ||||||||||
6 | Use the J 39200 in order to measure the resistance between the 6-way ABS brake motor pack connector terminal C and the ABS brake motor pack connector terminal D. Is the resistance within the specified range? | 0.2-1.5 ohms | ||||||||||
7 |
Refer to Checking Terminal Contact in the service manual. Are there signs of poor terminal contact or corrosion? | -- | ||||||||||
8 |
Does the DTC C1242 set during the last three ignition cycles? | -- | ||||||||||
9 | Replace the ABS brake motor pack. Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||||
10 | Place the correct wires into the connector cavities. Go to Antilock Brake System Connector End Views . Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||||
11 | Repair the open or high resistance in CKT 1284. Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||||
12 | Repair the open or high resistance in CKT 1285. Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||||
13 | Replace the terminals that exhibit signs of poor terminal contact or corrosion. Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||||
14 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||||
15 | The malfunction is intermittent or is not present at this time. Is the action complete? | -- | Go to Diagnostic Aids | -- |
