DTC C1255 With Various Sub Codes - keywords EBTCM ICCS TCS

This PI was superseded to update PI, removeing phone number to Delphi Tech support. Line has been disconnected and no longer in use for this concern. Please discard PIC4036.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Along with the C1255, a 2 digit Sub Code will set. The first digit is a Letter, and the 2nd digit is a number. Note that only the Tech 2 will display these sub codes, using the On Board Diagnostics through the Drivers Information Center on Cadillac and Corvette WILL NOT display sub codes.

Here is a list of the Sub Codes that may set:

E0, E1, E2, E3, E4, E5, E6, E7 M0, M1, M2, M3, M4, M5, M6, M7

Probable Cause: Each sub code represents a specific malfunction. Most sub codes set due to a malfunction internal to the EBTCM, and can be repaired by replacing the EBTCM. However, EBTCM replacement is NOT always necessary when DTC C1255 is set. Here is a list of exceptions where a fault external to the EBTCM will set C1255.

C1255 E2: This Sub Code may set due to a loss of battery or ground to the EBTCM.

1. Battery Cable disconnect
2. EBTCM Fuse Pull
3. EBTCM harness disconnect
4. Weak or Discharged battery
5. Any other interruption of battery or ground to the EBTCM

C1255 E2: Can also set when an EBTCM is first installed on a vehicle. C1255 E2 will be stored as a history code only, and WILL NOT turn on the ABS light. A typical service scenario is when an EBTCM is replaced for a DTC other than C1255. The vehicle again returns with the ABS light on, and C1255 E2 is set as a history DTC along with the original DTC which brought the vehicle in for service. The servicing technician is erroneously convinced that the new EBTCM is defective.

Replace the EBTCM for C1255 E2 only when a source of a battery disconnect cannot be identified and was not set due to EBTCM replacement.

C1255 M5: This Sub Code indicates that the EBTCM has detected a malfunction in the one of the Wheel Speed Sensor Circuits, and sets along with Wheel Speed Sensor DTCs (C1221 thru C1235). Disregard C1255 M5 and perform diagnostics for the other wheel speed DTCs. Only replace the EBTCM if all other wheel speed sensor diagnostics have been exhausted and the source of the DTCs cannot be identified.

C1255 E4 and E6 set together: This sub code combination sets when the pump motor ground circuit has detected B+. This condition can occur if the BPMV ground circuit is shared with other components and the ground bolt is loose or disconnected. These other components are seeking ground, then back-feed into the EBTCM thru the BPMV.

If the sub code(s) are included in one of the exceptions listed above, repair the external condition, then clear the code and verify that C1255 does not reset. If the sub code(s) are NOT one of the exceptions listed above, replace the EBTCM.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.