GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2008 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Engine 🢒 Engine Controls and Fuel - 6.6L 🢒 Engine Control Module Replacement

Notice: 

   • Turn the ignition OFF when installing or removing the control module connectors and disconnecting or reconnecting the power to the control module (battery cable, powertrain control module (PCM)/engine control module (ECM)/transaxle control module (TCM) pigtail, control module fuse, jumper cables, etc.) in order to prevent internal control module damage.
   • Control module damage may result when the metal case contacts battery voltage. DO NOT contact the control module metal case with battery voltage when servicing a control module, using battery booster cables, or when charging the vehicle battery.
   • In order to prevent any possible electrostatic discharge damage to the control module, do no touch the connector pins or the soldered components on the circuit board.
   • Remove any debris from around the control module connector surfaces before servicing the control module. Inspect the control module connector gaskets when diagnosing or replacing the control module. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion into the control module.
   • The replacement control module must be programmed.

Important: Before removing the engine control module (ECM), use the scan tool to capture the ECM data. This captured data will then need to be restored into the NEW ECM. Refer to Control Module References .

Removal Procedure

    Object Number: 1864631 Size: SH
  1. Using a scan tool, capture the ECM data.
  2. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection .
  3. Disconnect the engine wiring harness electrical connectors (3) from the ECM (1).

    4. Object Number: 1864632 Size: SH
  4. Disengage the 2 retaining tabs on the ECM bracket and remove the ECM.

    5. Object Number: 1864634 Size: SH
  5. Remove the ECM bracket nuts and bracket.

Installation Procedure

    Object Number: 1864634 Size: SH
  1. If the ECM bracket was removed, perform the following steps:

    2. Notice: Refer to Fastener Notice in the Preface section.

  2. Position the ECM bracket and install the bracket nuts.

    3. Tighten
    Tighten the nuts to 9 N·m (80 lb in).


    Object Number: 1864632 Size: SH
  3. Install the ECM under the bracket tabs and push down on the ECM engaging the 2 retaining tabs on the ECM bracket.

    4. Object Number: 1864631 Size: SH
  4. Connect the engine wiring harness electrical connectors (3) to the ECM (1).
  5. Connect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection .
  6. If a NEW ECM was installed, program the ECM. Refer to Control Module References .