Test Description

The numbers(s) below refer to the step number(s) on the diagnostic table.

1. 2. If the instrument panel tachometer is working properly, the cause of the malfunction is most likely between the PCM and the EBCM, or the EBCM itself.
2. 9. At this point, the PCM is likely causing the malfunction. Refer to OBD system check.
   Fig 1: DTC C0235-C0237 or P1504 (1 Of 2)

   Courtesy of GENERAL MOTORS CORP.

Fig 2: DTC C0235-C0237 or P1504 (2 Of 2)

Courtesy of GENERAL MOTORS CORP.