GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The IPC monitors the tachometer sent by the PCM through CKT 121 (WHT). The IPC software controls one of the following two display types:

    • A message display with a digital IPC
    • An analog gauge with an analog IPC, consisting of a needle pointer

The IPC interpolates and scales the tachometer information received from the PCM.

Diagnostic Aids

  1. Connect a scan tool to the DLC.
  2. Test for any set DTCs if no DTCs are set current.
  3. Test CKT 121 (WHT) for an open or short.