Tachometer Inaccurate

Circuit Description
The IPC monitors the tachometer sent by the PCM through CKT 121 (WHT). The PC software controls one of the following two display types:
^ A message display with a digital PC
^ 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.