If the ECM shorts out or stops working in your 2003 Monte Carlo, you have to replace it if you wish to keep driving the vehicle. The ECM is the computer that regulates everything the engine does. Without it, the engine cannot run because the computer tells the engine how much gas, air and spark it needs to properly run. Without the ECM, the engine will not even fire. Taking the vehicle to a dealership for repair can be very expensive. The cost makes it a perfect do-it-yourself job.
Open the hood on the Monte Carlo and disconnect the negative battery terminal.
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.
Remove the left side support brace from the outside of the air intake box with a 13-millimeter socket.
Remove the two bolts that hold the two halves of the air box together with an 8-millimeter socket.
Pull the air box out of the car to expose the ECM under the air intake box.
Remove the two bolts that secure the ECM to the fender well with an 8-millimeter socket.
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.
Place the new ECM into place and secure the bolts. Reconnect the electrical connectors. They are connected when you hear them snap into place.
Place the air intake box into the engine bay and secure the two pieces together with the original bolts.
Reconnect the left side support brace.
Place the air filter back into the air intake box and place the lid back onto the box.
Reconnect the negative battery terminal.
