P0320: How to Diagnose & Fix — Ignition/Distributor Engine Speed Input Circuit Malfunction

The 2.5L KL-DE V6 uses a cam-driven distributor with an internal O-ring/oil seal at the base and a shaft bushing. As the seal hardens with age, engine oil weeps up the shaft and pools inside the distributor cap, fouling the cap and rotor and shorting the ignition. On higher-mileage cars the shaft bushing also wears, allowing shaft wobble that both worsens the leak and disturbs the pickup signal. The result is a rough-running, misfiring, hard-starting or stalling V6 that many owners chase before finding the source. This is a well-known KL-engine quirk shared with the MX-6 and Ford Probe GT.

First-generation Proteges (and 1.5L second-gen cars) use a camshaft-driven distributor that houses the ignition pickup. With age these distributors suffer internal bearing wear and moisture intrusion past the seal, which corrodes the pickup and shaft. The result is a car that runs fine cold but stalls once hot and refuses to restart until it cools, or a sudden loss of spark and a crank-no-start. Documented cases include a 1990 Protege that ran ~10 minutes then abruptly stalled until cold (fixed by a dealer distributor replacement) and a 1.8L DOHC no-start where new coil, wires, cap and rotor did not cure it until the distributor was replaced.

The crankshaft position sensor on the 4.0L I6 and 2.5L I4 XJ is a classic thermal-failure item. Internal components and wiring degrade with age and heat, so the sensor works cold but drops signal once the engine reaches operating temperature. Without a CPS signal the PCM cuts spark and fuel, producing a stall or a crank-but-no-start that mysteriously 'fixes itself' after the engine cools. It is one of the most frequently discussed XJ failures in enthusiast communities and typically strikes around 125,000-175,000 miles.

The crankshaft position sensor (CKP) on the 4.7L (and 4.0L) Grand Cherokee commonly fails from heat-soak: it works when cold but its internal resistance rises when hot, so the PCM loses the crank signal and the engine won't restart until it cools 30-60 minutes, or it stalls randomly while driving. A cranks-but-no-start after a hot soak is the classic signature.

Libertys of both generations lose the crank reference signal to the PCM, setting P0320 and shutting the engine off without warning - owners describe the vehicle simply dying at speed, sometimes restarting immediately and sometimes not for hours, and often producing a limp-mode condition. The fault is heat-sensitive, so it typically appears after the engine is warmed and is hard to reproduce cold at a shop. The forum record contains a real diagnostic warning: on Chrysler powertrains, crank and cam sensor codes are misleading, and the failure is frequently in the connector or the harness (oil-contaminated pins, chafed wiring) or in the PCM rather than in the sensor itself - multiple owners report P0320 returning immediately after a new sensor. Stalling in traffic makes this a safety issue, not just a driveability complaint.