The powertrain control module on the 1997 Ford F-350 with the 7.3-liter Powerstroke diesel engine monitors the engine sensors and modifies the air-to-fuel ratio, as needed. It’s also responsible for sending the command to the injector driver module to fire each fuel injector. Replacing the PCM is pretty straightforward, but finding it is a little tricky, as it is in an unorthodox area. Unlike more modern vehicles, the 1997 F-350’s PCM requires no programming after installation, just a simple test drive to learn the vehicle and environmental conditions.
Open the F-350’s hood and look about halfway down the firewall, on the driver’s side. Find the rectangular component sticking out of the firewall with a large wiring harness connected to it, this is the powertrain control module.
Loosen the pinch bolt on the negative battery cable end on each battery, using a ratchet and socket, and disconnect the negative battery cable from each battery. Set the cable aside to prevent accidental reconnection.
Remove the bolt securing the wiring harness to the PCM, using a ratchet and socket. Pull the wiring harness from the PCM with a slight wiggling motion.
Unfasten the two nuts securing the PCM’s rubber seal, using a ratchet and socket. Remove the screws securing the rearmost part of the fender liner to the fender. Bend the fender inward to allow clearance for the PCM, then pull the PCM and seal from the firewall.
Remove the seal from the old PCM and slide it onto the new PCM, aligning the seals mounting holes with those on the PCM.
Bend the fender liner inward and slide the PCM and seal into place in the firewall mounting studs. Hand-thread the PCM and seal retaining nuts, then torque them to between 27 and 35 inch-pounds, using an inch-pound torque wrench and socket.
Align the fender liner with its mounting holes on the fender and snug the screws with a ratchet and socket.
Plug the wiring harness into the new PCM and tighten its retaining bolt to 35 inch-pounds. Reconnect the negative battery cables and tighten their pinch bolts with a ratchet and socket.
Start the F-350’s engine and drive it as you normally would for approximately 10 miles. The PCM does not require any programming, but it does require a relearn procedure, which is what this initial drive does. During this relearn procedure, you will likely experience abnormal engine and transmission performance.
