1999 Jeep Cherokee XJ 4.0 AW4 automatic: I’m chasing an intermittent crank/no-start and random stall issue where I keep getting P0320 (crankshaft sensor circuit/ignition reference). Sometimes it will start and run perfectly (no noises/codes), including one time right after installing a replacement CKP. At one point opening/closing the driver door would bog/stall the engine and then it would crank/no-start again; I crawled out the trunk to make sure it was the door and I’m not losing my mind. I found the driver door jamb switch connector was heavily corroded and had it replaced. It also bogged/died when put into reverse (suspect the NS Switch? unsure if related). I did have a security system with remote start installed by a local shop a year prior and it drove fine until the cel came on. What I’ve done: NTK CKP (Mopar discontinued the part and read that NTK manufactured the part for Mopar), NTK cam/distributor pickup sensor, ignition coil, distributor cap/rotor (no play so I ruled out a bad distributor), copper plugs and wires; all grounds cleaned/tightened including dipstick ground. Im getting fuel pressure and the pump primes for 2-5 seconds. Checked the ASD relay. I did a Big 7 cable set with thicker gauge wiring and new 4 hole injectors from KSuspension. I found it was running rich, I assume because I wasn’t able to put enough miles on after resetting the PCM so it can relearn the a/f ratio. I verified ~5.3V reference present at the CKP connector. What else am I missing? Could it be a shot PCM? I’m at my wits end and would love any advice on what to do next.

 

You’ve got a dying PCM. Classic XJ P0320 that won’t go away after all that work means the internal driver for the crank signal is failing. The door jamb thing was a distraction. Get a rebuilt PCM from a known XJ specialist like Flagship One or All Computer Resources. Make sure they flash it for your VIN and auto trans. Don’t waste more time on sensors.

 

Before you buy a refurbished PCM, carefully check the wiring, plugs and grounds. Spray electrical contact cleaner into the plugs at your PCM and the one at the CPS. A loose connection may be aggravated by slamming a door. Put a VOM on the CPS to confirm you didn't get a bad one. I've had the best luck with the Standard brand in the red boxes at parts store.