Do not automatically assume that a PCM is to blame for hard start, no start, stalling, or other driveability concerns. PCM failures are not uncommon, but other problems that produce the same symptoms are much more common. Unfortunately, there is not a specific way to diagnose a PCM and symptoms of a PCM fault can vary greatly. Process of elimination is your greatest tool - before looking into a PCM replacement, the following system checks should be performed:
• Verify battery condition (12.5 - 12.7 volts for a fully charged battery in good working condition). While this seems like a rudimentary recommendation, it should be done nonetheless - you'd be surprised at how often batteries are overlooked because they are "not that old" or "read 12 volts".
• Verify glow plug condition and check for proper glow plug operation. See 6.0L Power Stroke glow plug system troubleshooting guide for additional information.
• Verify ICP sensor readings are accurate and IPR valve duty cycle is within spec. If actual ICP varies significantly from desired ICP and/or the IPR valve duty cycle is high while the engine is running, suspect a sensor failure, high pressure oil leak, or high pressure oil pump related problem.
• Verify FICM voltage is within spec (47 - 48 volts is ideal, > 45 is acceptable). See 6.0L Power Stroke FICM test procedures for additional information.
• Trace the engine wiring harness and check for wire chaffing. The harness leans against various sharp corners, bolts, and studs that can puncture it overtime (improbable for intermittent conditions but a common issue nonetheless). It is especially important to check the FICM connectors and harness around the FICM.
• Verify CPS (camshaft position sensor) and CKP (crankshaft position sensor) signals are in sync. A lost or out of sync signal will cause intermittent stalling, hard start, and no start issues. CKP sensors are rarely a problem on a 6.0L Power Stroke. If codes P2617 and P2614 are set simultaneously, this may not be a sensor issue. These codes are often set together following a long (excessive) crank condition.
If all systems check out, a PCM fault is a strong possibility. A Ford dealer will charge you an arm, a leg, and your first born to replace a PCM. You can purchase a remanufactured unit for under $400 USD with the latest factory Ford flash and a lifetime warranty. As you'll see in the procedures below, replacing the PCM is not a daunting task.
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• Disconnect both negative battery cables. DO NOT attempt to replace a PCM without disconnecting the negative battery cables.
• Remove the driver side positive battery cable, then completely remove the driver side battery from the vehicle. The factory battery terminals and the battery hold-down bracket use an 8 mm socket.
• The PCM is mounted to the driver side fender and it will become accessible with the battery completely removed.
• Carefully remove the (3) PCM connectors. The connectors feature a unique clip that must be fully released to free the connector from the PCM (see image for details of fully engaged and fully disengaged positions). Once the retaining clip is completely released, simply pull the connector outwards to disconnect it from the PCM; it should come off with ease is the locking clip is fully disengaged.
• With the PCM connectors removed, remove the PCM - it is held in place by (2) bolts requiring a 10 mm socket (one towards the firewall, another towards the grille). Once the hardware has been removed, pull it upwards; a small clip on the bottom of the PCM secures the bottom edge, but does not require any intervention during removal.
• While the PCM is removed, check for wiring chaffing on all three connector harnesses! It is common for the harness to chafe on the battery box. If you find a bare wire, bare wires, of even if the wire loom shows signs of wear, perform any necessary repairs before continuing. A few wraps of electrical tape can provide years of protection if it seems as though the protective wire loom has been compromised.
• Reinstall the PCM in the reverse manner. Apply a small amount of dielectric grease to each pin on the connectors of the new PCM.
• The PCM connectors are odd in that the connector slips into the PCM but does not fully seat until the connector clip is engaged - pay attention the images we've included so that you may ensure that the connectors are fully seated.
• Reinstall the driver side battery, reconnect the negative battery cables, and test start the vehicle. If the engine does not start and/or you're dash lights up like a Christmas tree, retrace your steps; you may have not gotten a connector installed properly.