GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2005 🢒 GMC C Sierra - 2WD 🢒 Engine 🢒 Engine Controls - 6.6L (LLY) 🢒 Engine Control Module Replacement

Service of the engine control module (ECM) should consist of either replacement of the ECM or programming of the electrically erasable programmable read only memory (EEPROM). If the diagnostic procedures call for the ECM to be replaced, the replacement ECM should be checked to ensure that the correct part is being used. If the correct part is being used, remove the faulty ECM and install the new service ECM.

Removal Procedure

Important: 

   • To prevent internal ECM damage, the ignition switch must be OFF when disconnecting or connecting power to the ECM.
   • Remove any debris from the ECM connector surfaces before servicing the ECM. Inspect the ECM module connector gaskets when diagnosing or replacing the ECM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion into the ECM.
   • The replacement ECM must programmed.

    Important: It is necessary to record the remaining engine oil life. If the replacement module is not programed with the remaining engine oil life, the engine oil life will default to 100%. If the replacement module is not programmed with the remaining engine oil life, the engine oil will need to be changed at 5000 km (3,000 mi) from the last engine oil change.

  1. Using a scan tool, retrieve the percentage of remaining engine oil. Record the remaining engine oil life.

    2. Object Number: 1334384 Size: SH
  2. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.
  3. Disconnect the ECM electrical connectors (2).

    4. Object Number: 1334382 Size: SH
  4. Release the ECM cover retaining tabs.
  5. Remove the ECM cover from the bracket.
  6. Remove the ECM cover.

Installation Procedure

    Object Number: 1334382 Size: SH
  1. Install the ECM.

    2. Important: The cover must be fully installed prior to the electrical connections being made to ensure the ECM is fully seated in the bracket.

  2. Install the ECM cover to the bracket.
  3. Engage the ECM cover retaining tabs.

    4. Object Number: 1334384 Size: SH
  4. Connect the ECM electrical connectors (2).
  5. Connect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.
  6. If a NEW ECM was installed, program the ECM. Refer to Control Module References in Computer/Integrating Systems.
  7. Perform the turbocharger learn procedure. Refer to Turbocharger Learn .