P0320

P0320 indicates a fault in the ignition or distributor engine speed input circuit — on modern engines this means the crankshaft position sensor signal to the ECM is intermittent or malformed. The ECM uses this signal for ignition timing, fuel injection timing, and misfire detection, so a P0320 typically pairs with crank-no-start symptoms, intermittent stalling, or random misfire codes. Diagnostic ladder: visually inspect the CKP sensor connector (oil and dirt accumulation is the #1 cause on cars above 80K miles), check sensor resistance (most magnetic-pickup sensors read 500-1500 ohms; Hall-effect sensors are 3-wire with 5V reference and you should see a clean square wave on a scope at cranking speed). Wiggle-test the harness from the sensor to the ECM with the engine running — if RPM drops out or the code freshly logs, you have a wiring fault. Caveat: P0320 sometimes traces back to a failing alternator dumping AC ripple onto the ECM 5V reference — measure alternator AC output with a multimeter (should be under 50mV AC); higher means the diode pack is failing and faking sensor circuit faults.

Vehicle-specific patterns: Chrysler/Dodge 3.5L V6 (300M, Intrepid, Concorde, 1998-2004) — CKP sensor failure from heat-soak is the textbook P0320; sensor lives on the bellhousing and gets cooked by exhaust manifold radiation, $40-80 part. Subaru EJ25 (Impreza, Forester, Outback, 2005-2014) — CKP sensor connector corrosion at the front of the engine; the connector sits in the splash zone and copper-greens. Volkswagen 1.8T (Jetta, Passat, Audi A4 B5/B6, 1997-2005) — wiring harness chafe at the back of the engine where it crosses the intake manifold; intermittent P0320 with no-start hot. GM 3.8L 3800 Series II V6 (Buick, Pontiac, Olds, 1995-2005) — CKP sensor magnetic pickup fails from oil contamination at the sensor seal. Estimated repair: $80 to $380.