Circuit Description
DTC 1256 identifies an ABS motor that cannot energize due to an open in the ABS motor circuitry. The malfunction will not allow proper front ABS operation.
Conditions for Setting the DTC
DTC C1256 can only set when the motor is commanded off. A malfunction exists if the EBCM/EBTCM detects an out of range voltage on either of the left front ABS motor circuits. The out of range voltage on either circuit indicates an open circuit exists.
Action Taken When the DTC Sets
| • | An open ABS motor will not activate. |
| • | A malfunction DTC stores. |
| • | The ABS/TCS disables. |
| • | The amber ABS/TCS warning indicators turn on. |
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTC function is used. |
| • | 100 drive cycles pass with no DTC detected. |
Diagnostic Aids
Use the Scan Tool Manual Control function in order to exercise ABS motor movement of affected channel in both directions while applying light pressure on the brake pedal. An intermittent malfunction may be indicated if erratic or jumpy brake pedal movement is detected while performing an apply or release function of the ABS monitor. Use the enhanced diagnostic function of the Scan Tool in order to measure the frequency of the malfunction. Refer to the Scan Tool manual or Scan Tool Diagnostics located in this section for the procedure. If the malfunction is not current, use the following procedure to pinpoint an intermittent malfunction in the motor circuitry or connections:
- Wiggle the wires of the affected channel.
- Inspect if the DTC resets.
Thoroughly inspect any circuitry that may be causing the intermittent complaint for the following conditions:
| • | Rubbed-through wire insulation |
| • | A broken wire inside the insulation |
| • | Backed out terminals |
| • | Improper mating |
| • | Broken locks |
| • | Improperly formed or damaged terminals |
| • | Poor terminal-to-wiring connections |
| • | Physical damage to the wiring harness |
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.
Step | Action | Value(s) | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Diagnostic System Check performed? | -- | Go to Diagnostic System Check | |||||||||||||
2 |
Does DTC C1256 occur intermittently? | -- | Go to Diagnostic Aids | Go to Step 3 | ||||||||||||
3 |
Is the resistance within the specified range? | 0.2-1.5ohms | Go to Step 4 | Go to Step 8 | ||||||||||||
4 |
Is continuity present in CKT 1280 between the 6-way ABS brake motor pack connector and the 8-way EBCM/EBTCM connector C2? | -- | Go to Step 5 | Go to Step 9 | ||||||||||||
5 | Use the J 39200 in order to measure CKT 1281 for continuity between the 6-way ABS brake motor pack connector terminal E and the 8-way EBCM/EBTCM connector C2 terminal H. Is continuity present in CKT 1281 between the 6-way ABS brake motor pack connector and the 8-way EBCM/EBTCM connector C2? | -- | Go to Step 6 | Go to Step 10 | ||||||||||||
6 |
Is there evidence of poor terminal contact and corrosion? | -- | Go to Step 11 | Go to Step 7 | ||||||||||||
7 |
Does DTC C1256 set as a current DTC during the last three drive cycles? | -- | Go to Step 12 | Go to Step 13 | ||||||||||||
8 | Replace the ABS brake motor pack. Refer to ABS Motor Pack Replacement . Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||||||||
9 | Repair the open or high resistance in CKT 1280. Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||||||||
10 | Repair the open or high resistance in CKT 1281. Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||||||||
11 | Replace all of the terminals or the connectors that exhibit signs of poor terminal contact, corrosion, or damaged terminal(s). Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||||||||
12 | Replace the EBCM/EBTCM. Refer to Electronic Brake and Traction Control Module Replacement . Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||||||||
13 | The malfunction is intermittent or not present at this time. Is a concern still present? | -- | Go to Diagnostic Aids | Go to Diagnostic System Check |
