How to Replace a 2003 Monte Carlo ECM
- 1). Open the hood on the Monte Carlo and disconnect the negative battery terminal.
- 2). Remove the lid from the air intake box and pull the air filter out of the box. The ECM is located on the bottom of the air intake box.
- 3). Remove the left side support brace from the outside of the air intake box with a 13-millimeter socket.
- 4). Remove the two bolts that hold the two halves of the air box together with an 8-millimeter socket.
- 5). Pull the air box out of the car to expose the ECM under the air intake box.
- 6). Remove the two bolts that secure the ECM to the fender well with an 8-millimeter socket.
- 7). Remove the electrical connectors from the ECM by pulling on them. Each connector fits into one slot only so there is no need to label them.
- 8). Place the new ECM into place and secure the bolts. Reconnect the electrical connectors. They are connected when you hear them snap into place.
- 9). Place the air intake box into the engine bay and secure the two pieces together with the original bolts.
- 10
Reconnect the left side support brace. - 11
Place the air filter back into the air intake box and place the lid back onto the box. - 12
Reconnect the negative battery terminal.
Source...