TDC Offset Program Procedure

WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1994 GMC Vandura Special, 1994 GMC Vandura, 1994 GMC Rally Camper Special, 1994 GMC Rally, and 1994 GMC Forward Control. However, it is still accessible from the selected car via links, so may be relevant.

This procedure allows the PCM memory to be updated with the correct TDC offset for the vehicle.

DTC 88 will be stored until this procedure has been completed Set up:

Battery is fully charged.
Engine operating at idle.
Vehicle at operating temperature.
Connect Tech 1 Scan Tool
Select "OUTPUT TESTS" and "INJ. PUMP"
Activate "TDC LEARN"
NOTE: It takes PCM 20 seconds to learn TDC offset.
Verify "TDC OFFSET" in data list.
DTC 88 will be stored if procedure has not been done correctly.
NOTE: If the PCM fails to program the TDC OFFSET, do the following:
Check all PCM connections.
Check Techline terminal/equipment for latest software version.
Try again to program the PCM. If it fails again replace the PCM.