GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 Chevy C Silverado - 2WD 🢒 Engine 🢒 Engine Electrical 🢒 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: 877692 Size: SH
  2. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.
  3. If equipped with the Allison transmission regular production option (RPO) M74, remove the engine harness clip from the ECM cover.

    4. Object Number: 814118 Size: SH
  4. Release the ECM cover mounting tabs.
  5. Release the ECM cover from the mounting bracket.
  6. Remove the ECM cover.

    7. Object Number: 877694 Size: SH
  7. Loosen the ECM electrical connector bolts (2).
  8. Disconnect the ECM electrical connectors (3).

    9. Object Number: 877695 Size: SH
  9. Release the spring latch from the ECM.
  10. Release the ECM mounting tabs from the ECM.
  11. Remove the ECM.

Installation Procedure

    Object Number: 877695 Size: SH
  1. Install the ECM.

    2. Ensure that the mounting tabs are engaged.

  2. Secure the spring latch to the ECM.

    3. Object Number: 877694 Size: SH
  3. Connect the ECM electrical connectors (3).

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

  4. Tighten the ECM electrical connector bolts (2).

    5. Tighten
    Tighten the bolts to 8 N·m (71 lb in).


    Object Number: 814118 Size: SH
  5. Install the ECM cover.

    6. Object Number: 877692 Size: SH
  6. If equipped with the Allison transmission RPO M74, install the engine harness clip to the ECM cover.
  7. Connect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.
  8. If a NEW ECM was installed, program the ECM. Refer to Service Programming System (SPS) in Programming.