GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC K Pickup - 4WD (CNG) 🢒 Engine 🢒 Engine Controls - 5.0L and 5.7L 🢒 Engine Control Unit Replacement

Removal Procedure

    Object Number: 478943 Size: SH

    Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

  1. Disconnect the negative battery cable.
  2. Press the mounting adapter clip (5) away from the AF ECU (6).
  3. Lift the AF ECU from the mounting adapter.
  4. Disconnect the connectors (1,2) from the AF ECU.

Installation Procedure

    Object Number: 478943 Size: SH

    Important: The AF ECU must be programmed (flashed) before attempting to start the vehicle.

  1. Connect the connectors (1,2) to the AF ECU (6).
  2. Install the rearward side of the AF ECU into the mounting adapter rear clips.
  3. Press down on the AF ECU until the mounting adapter clip (5) snaps over the AF ECU.
  4. Connect the negative battery cable.