The 1999 Chevy Cavalier engine control computer is a common source of drive problems. Its mounting location exposes it to dirt and moisture from the outside that leads to corrosion and eventual failure. Symptoms such as stalling, idle speed fluctuation, overheating and failure to start can many times be traced to a faulty engine control computer. Replacement is straightforward and requires no specialty tools to accomplish. This repair can be accomplished in less than one hour by a well equipped home mechanic.
Apply the parking brake. Loosen the lug nuts on the right front wheel and raise the right front wheel off the ground using the floor jack. Place jack stands under the right front of the subframe. Lower the car onto the stand and remove the floor jack. Remove the right front wheel.
Remove the inner splash shield using a 10mm socket to remove the mounting bolts and a needle nose pliers to remove the plastic trim retainers. Pull the inner splash shield out of the fender well. Remove the 13mm bolt that attaches the horn to the frame of the car and unplug the electrical connector on the horn. Set the horn aside.
Remove the 8mm retaining screws that attach the computer to the computer bracket. Detach the electrical connectors from the computer and slide the computer from the bracket and out of the fender well.
Clean any debris off of the outside of the computer and remove the two 5.5mm retaining screws that attach the EPROM cover to the computer housing. Squeeze together the two retaining tabs on the EPROM, located inside the computer housing, and remove the EPROM from the old computer. Transfer the e-prom into the new computer and reinstall the cover.
Install the new computer into the bracket in the fender well. Reinstall the horn and inner fender well splash shield. Reinstall the wheel and lower the car to the ground.
Start the engine and hold a high idle speed by holding the gas pedal down slightly, for a few minutes. Release the gas pedal very slowly until the computer can control idle speed on its own. This is the beginning of the relearn procedure for the computer. Test drive the Cavalier for approximately 30 minutes in a variety of driving situations such as stop and go traffic and highway speeds to complete the relearn process and to verify that the repair is complete.
