How to Replace a PCM on Vehiclesby Contributing WriterUpdated June 12, 2017
The PCM, power train control module, within your Vehicles manages the engine control system. Replacement of the PCM is not very common, but when your Vehicles is diagnosed with a failing PCM it's important to replace it immediately to ensure the Vehicles continues to operate. The PCM is a silver box with large electrical connectors coming from it. You can replace the PCM without the help of a mechanic, but you must first purchase the correct PCM Vehicles your car.
Under The Hood:
- How to Replace a PCM on a Wrangler
- How to Replace the PCM in an '04 Sebring
- How to Replace the PCM on a PT Cruiser
- How to Replace the PCM in a 2003 Focus
Disconnect the negative battery cable from the battery with a wrench or socket and ratchet. Isolate the cable end so that it cannot fall back against the battery.
Locate the powertrain control module or PCM on the firewall of the Jeep. Remove the three plastic covers from the 32-pin connectors on the face of the PCM. The covers snap onto the connectors and come off the same way.
Unplug the three 32-pin connectors from the PCM, being careful not to bend the pins or damage the plug. The connectors will pull straight out from the PCM but you may need to wiggle the connector a little as they are a tight fit.
Remove the three mounting bolts that anchor the PCM to the firewall of the Jeep with a socket and ratchet. Position the new PCM on the fire wall and use the mounting bolts from the old one to secure it. Tighten the bolts to 35 inch-pounds with a torque wrench.
Carefully install the three 32-pin connectors into the plugs on the face of the PCM. Install the connector caps by snapping them in place.
Reinstall the negative battery cable onto the battery and tighten the retaining bolt with a wrench or socket and ratchet. A DRB scan tool must be connected to the PCM after installation to set the vehicle identification number and the original mileage of the Jeep so the odometer will read correctly.
Items you will need
DRB scan tool
Open the hood and remove the battery negative cable from the driver’s side strut tower by using a wrench. Isolate the cable end so it will not contact any metal. To be safe, allow 10 minutes for the circuits to go to sleep before proceeding.
Locate the PCM on the driver’s side between the radiator support and the strut tower. Remove the bolts securing it to the mounting bracket by using a socket.
Push the arm locks down on each wire connector and pull the connector straight out of the PCM. Remove the PCM from the car.
Install the new PCM. Make sure the mileage and VIN number are first programmed into the PCM. There is a school of thought that static electricity from clothing or the weather is sufficient to harm a PCM. Whether this is accurate or not, there is no reason to test the validity of these comments so just lean against the car and touch a finger to the engine block to dissipate any possible static electrical charge. Better safe than sorry.
Position the PCM so the electrical connectors can be installed. Be careful to first make sure to install the right one in the right slot by comparing the hole and number of pins. Push each connector in gently and completely straight to prevent any of the pins from becoming bent. Flip the lower arm up to lock them in place.
Position the PCM on the bracket and install the bolts. Install the negative battery cable to the stud on the shock tower.
Items you will need
Set of sockets
Remove the key from the ignition. Open the hood and support it with the hood prop.
Using a flat screwdriver, loosen the intake air hose clamp at the air cleaner housing, and disconnect the hose from the housing outlet. Lift up slightly on the air cleaner, and remove the air inlet duct from the housing. Lift the housing up and out of the engine compartment.
Loosen the negative battery cable terminal pinch bolt, using a ratchet and socket. Rotate the terminal slightly to break it loose from the battery post, then disconnect the terminal from the battery. Lay the cable aside where it cannot accidentally make contact with the negative battery post.
Locate the PCM assembly on the driver-side firewall, near the brake master cylinder. Lift up on the lock tabs on the electrical connectors, and disconnect the PCM from the vehicle wiring harness.
Using a ratchet and socket, remove the three PCM bracket retainer bolts and pull the bracket off the firewall. Turn the assembly over and, using a ratchet and socket, remove the four retainer nuts. Separate the old PCM from the bracket.
Position the new PCM on the bracket. Install the retainer nuts and torque them to 95 inch-pounds, using an inch-pound torque wrench and socket.
Position the PCM assembly on the firewall. Install and torque the retainer bolts to 35 inch-pounds. Plug the electrical connectors in, and ensure that the lock tabs snap securely into place.
Install the negative cable terminal on the negative battery post. Torque the terminal pinch bolt to 110 inch-pounds.
Lower the air cleaner housing into place. Install the fresh air inlet duct in its port in the housing, and slip the intake air hose over the outlet port on the housing. Tighten the intake air hose clamp securely.
Items you will need
Inch-pound torque wrench
Place the Focus in "Park" and remove the key from the ignition. Never attempt to work on an electronic component such as the PCM with the key in the ignition.
Open the passenger glove box; squeeze the left and right side of the glove box until the glove box door disengages. You will now see the PCM. Remove the glove box door completely by removing the three screws along the bottom. Remove any trim or carpet needed to access the PCM by moving it out of the way.
Remove the wiring harness bolt using a 10mm socket; the bolt is found on the top of the PCM. Disconnect each electrical connection by simply pulling them out of the PCM. Detach the PCM securing bracket. Unscrew any screws that are securing the PCM to the mount. Slide the PCM out of the mount.
Slide the new PCM into place. Replace the screws to secure the new PCM to the mount. Plug the securing bracket back into place to ensure the PCM is secured. Replace the mounting bolt using the 10mm socket.
Reinstall the glove box by sliding it back into place. Replace the three screws and tighten to secure the glove box to the vehicle. Close the glove box door. The PCM is now replaced and ready for use.
Items you will need