GM Service Manual Online
For 1990-2009 cars only

Important: Oil life must be recorded by the mechanic before the PCM is replaced so it can be reprogrammed into the PCM. The Capture Info function on the scan tool will not record oil life or the Clear DTC function on the scan tool will not clear (reset) the Oil Life. Refer to Oil Life Reset in this section.

Important: Switching a PCM from vehicle to vehicle will cause the memory data (Oil Life, Glow Plug System Type, VTD and TDC Offset) to follow the PCM. A VTD (Passlock) password learn must be performed for the vehicle to start. If the PCM remains in the vehicle, all the memory data must be relearned, treat the PCM as a Reprogrammed PCM except for TDC Offset (manual TDC Offset learn procedure must be performed).

If the diagnostic procedures call for the PCM to be reprogrammed or replaced then programming the EEPROM (memory data) in the PCM will be necessary. Use the procedures listed at the bottom of this section.

Removal Procedure


    Object Number: 398141  Size: SH
  1. Disconnect the negative battery cables.
  2. Remove the PCM protective cover (2).

  3. Object Number: 398166  Size: SH
  4. Release the PCM (2) retainer clip (4).
  5. Tilt the upper end of the PCM out of the mounting bracket and then lift the PCM out.
  6. Loosen the PCM connector mounting bolts (it is not necessary to completely remove the connector mounting bolts).
  7. Important: To prevent possible electrostatic discharge to the PCM, do not touch the component leads.

  8. Disconnect the PCM connectors.

Installation Procedure


    Object Number: 398166  Size: SH
  1. Install the PCM connectors.
  2. Tighten the connector mounting bolts.
  3. Slide the PCM into the mounting bracket (3) bottom end first.

  4. Object Number: 398183  Size: SH
  5. Engage the PCM retainer clip (4).

  6. Object Number: 398141  Size: SH
  7. Install the PCM protective cover (2).
  8. Connect the negative battery cables.
  9. The MIL, the antilock and the brake lamps will continue to be enabled until the PCM is programmed. Once the programming is complete, the lamps will be turned OFF and the normal operation will occur.

  10. Go to Programming the PCM.

Programming the PCM

Follow all of the procedures that are listed in the specific category listed below that best describes the repair performed.

PCM Replaced (New)

  1. Program "Flash" the PCM.
  2. Operate vehicle to 170°F (77°C). TDC Offset auto lean being performed.
  3. Reset Oil Life.

Reprogrammed PCM (Flash)

  1. Operate vehicle to 170°F (77°C). TDC Offset auto lean being performed.
  2. Learn Glow Plug System Type.
  3. Reset Oil Life.

Disconnected PCM/Reuse
Memory OK.

PCM Programming Procedure

  1. Perform the following set up:
  2. • The battery is charged.
    • The ignition is ON.
    • The data link connector is attached.
  3. Perform the programming. Refer to an up to date Techline terminal/equipment for user instructions.
  4. If the PCM fails to reprogram, do the following:
  5. • Check all of the PCM connections.
    • Check the Techline terminal/equipment for the latest software version.
    • Try again to reprogram the PCM. If the reprogramming fails again, replace the PCM. Refer to PCM replacement.

Glow Plug System Type Learn Procedure

Important: Vehicle must be in operating condition before performing this procedure.

  1. Using the scan tool, select Special Functions, Engine Output Functions and Glow Plug System Learn.
  2. Activate the Glow Plug System Learn by selecting ON. After the learn function has been preformed Not Learned will be displayed on the scan tool (in this step, the scan tool is clearing the system type).
  3. Go back to the Special Functions menu and select Glow Plug.
  4. Activate the Glow Plug system by selecting ON (in this step, the glow plug relay is now sending the identifying (signature) voltage to the PCM).
  5. The PCM will now be able to indentify the coorect glow plug system type. For visiual verifaction of the glow plug system, refer to Component Views.
  6. Clear the DTC P0380.
  7. Allow the PCM to power down for at least 45 seconds.
  8. Turn the ignition on leaving the engine off. Using the scan tool verify that DTC P0380 has not reset.
  9. If DTC P0380 reset, perform the following:
  10. • Check the connections at the glow plug relay.
    • Try again to relearn the glow plug system. If the relearn fails again, refer to P0380.

Reset Oil Life

Scan Tool

  1. Select Oil Life on the scan tool.
  2. Input the value in one percent increments.
  3. Select reset.
  4. Verify that the oil life index has been recorded.

Accelerator Pedal

  1. Turn the ignition switch to the ON position leaving the engine off .
  2. Push the accelerator pedal to the wide open throttle position 4 times in 5 seconds (oil life will reset to 100 percent) .
  3. Verify that the change oil message has been cleared.

TDC Offset Auto Learn

Important: The PCM will only perform an auto learn when a TDC Offset is not present (new/reflashed PCM).

The PCM will automatically activate the TDC Offset program when the engine coolant is greater than 77°C (170°F) and engine rpm is less than 900 (a momentary engine stumble will occur once the engine has reached the desired temperature and rpm, this is an indication that PCM auto learn function has been activated). It is possible that a 0.00 TDC Offset can be achieved. If the TDC Offset is programed out of range, a DTC P1214 will set.