The Powertrain Control Module is a vehicle's central computer. A malfunctioning PCM can cause a number of problems with the car, and you should replace it once you are sure it is the cause. Replacing the PCM on a Chrysler PT Cruiser is simpler than other vehicles because the module is mounted directly onto the engine firewall. The biggest concern, when installing a PCM, is the static electricity that can build up in your body as this can seriously damage the computer within the module.
Place the new module on an anti-static pad prior to installation to avoid static damage.
Disconnect the PT Cruiser's battery by loosening the cable clamp for the black negative cable with a wrench.
Put on an anti-static ground strap to help prevent static damage to the PCM. These are available at computer or electronics retailers. Connect the strap to your wrist and connect the strap's alligator clip to a metal ground on the car.
Pry off the clip for the wiring harness to the control module with a forked trim tool then move the harness away from the module.
Remove the retaining bolts to the Powertrain Control Module with a wrench then move the module away from the firewall. Disconnect the electrical connectors by pressing their side tabs then remove the module.
Connect the electrical connectors to the replacement module and install it onto the firewall with the bolts, making sure you don't touch the module's electrical terminals. Connect the wiring harness with its clip.
Reconnect the negative battery cable with the wrench.
An on-board diagnostic scan tool can help determine if the PCM is the cause of the car's problems. Look over your tool's complete instructions for which trouble codes indicate a bad PCM.