Circuit Description
DTC 1258 identifies an ABS motor circuit that shorts to voltage or an ABS motor that has low or no resistance. The malfunction will cause one of the following conditions to occur:
| • | The ABS motor will not be controlled at the commanded current rate. |
| • | The ABS motor will turn in the opposite direction or not at all. |
Conditions for Setting the DTC
DTC C1258 can set only when the ABS 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. An out of range voltage on either circuit indicates one of the following conditions:
| • | A circuit shorts to voltage. |
| • | An ABS brake motor shorts internally. |
Action Taken When the DTC Sets
| • | 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 Step 2 | |||||||||||||
2 |
Does DTC C1258 occur intermittently? | -- | Go to Diagnostic Aids | Go to Step 3 | ||||||||||||
3 |
Is any voltage present on CKT 1280 during this test? | -- | Go to Step 10 | Go to Step 4 | ||||||||||||
4 | Use the J 39200 in order to measure the voltage between the 6-way ABS brake motor pack harness connector terminal E and ground. Is any voltage present on CKT 1281 during this test? | -- | Go to Step 11 | Go to Step 5 | ||||||||||||
5 |
Is the resistance equal to the specified value? | OL (Infinite) | Go to Step 6 | Go to Step 12 | ||||||||||||
6 | Use the J 39200 in order to measure the resistance between the 6-way ABS motor pack connector terminal F and the 6-way ABS motor pack connector terminal E. Is the resistance measured equal to or greater than the specified range? | 0.2ohms | Go to Step 7 | Go to Step 9 | ||||||||||||
7 |
Is there damage which may result in a short to voltage? | -- | Go to Step 13 | Go to Step 8 | ||||||||||||
8 |
Did DTC C1258 set as a current DTC in the last three drive cycles? | -- | Go to Step 14 | Go to Step 15 | ||||||||||||
9 | Replace the ABS motor pack. Is the repair complete? | -- | -- | |||||||||||||
10 | Repair the short to voltage in CKT 1280. Is the repair complete? | -- | -- | |||||||||||||
11 | Repair the short to voltage in CKT 1281. Is the repair complete? | -- | -- | |||||||||||||
12 | Repair the short between CKT 1280 and CKT 1281. Is the repair complete? | -- | -- | |||||||||||||
13 | Replace all of the following components that are damaged:
Is the repair complete? | -- | -- | |||||||||||||
14 | Replace the EBCM/EBTCM. Is the repair complete? | -- | -- | |||||||||||||
15 | The malfunction is intermittent or not present at this time. Is a concern still present? | -- | Go to Diagnostic Aids |
