OBD-II Code P0338 — What It Means & How to Fix It

What Does This Error Mean?

P0338 means the crankshaft position sensor circuit is reading a voltage that is too high. The crankshaft position sensor tells the ECM exactly where the pistons are and how fast the engine is spinning. A high voltage reading means the ECM is getting bad data from this critical sensor. This can cause rough running, hard starting, stalling, or a no-start condition. P0338 needs to be repaired promptly — the crankshaft position sensor is not optional.

Affected Models

All vehicles 1996+
Common in GM vehicles (Chevrolet, GMC, Cadillac)
Common in Ford and Lincoln vehicles
Common in Chrysler, Dodge, Ram, and Jeep
Common in European vehicles with crankshaft-based ignition management

Common Causes

Short to voltage in the crankshaft position sensor signal wire
Failed crankshaft position sensor with an internal fault producing excessive output voltage
Damaged wiring insulation allowing the signal wire to contact a 5V or 12V power wire
Corroded connector causing pin-to-pin bridging between the signal and power terminals
ECM circuit fault providing incorrect reference or pull-up voltage on the sensor circuit

How to Fix It

Use an OBD-II scanner to confirm P0338 and check for other codes. P0336 (range/performance) or P0335 (circuit malfunction) alongside P0338 suggests multiple levels of failure. If you also have misfire or timing codes, the ECM is already struggling to manage the engine.

Record all codes before clearing — this tells the full story of the fault.
Locate the crankshaft position sensor connector and unplug it. With the ignition key ON (engine off), use a multimeter to test the signal wire for voltage. If it reads battery voltage (12V) or 5V reference with the sensor unplugged, there is a short to power in the wiring.

The signal wire should read near 0V or at most a very small pull-up voltage when the sensor is disconnected.
Inspect the wiring harness for the crankshaft position sensor. Look for areas where the wire might contact a power source — near the ignition coil, injector wiring, or any area where bundles cross. Look for chafed insulation where the harness rubs against the engine block or brackets.

Pay attention to heat-damaged areas near the exhaust — insulation that has hardened and cracked can allow wire contact.
Test the crankshaft position sensor itself. Unplug the connector and test the sensor according to your service manual. For magnetic sensors, test resistance across the signal terminals. For Hall effect sensors, check for internal shorts between signal and power or ground pins.

A failed Hall effect sensor with an internal short to power will produce a constant high voltage on the signal wire.
If the sensor tests good and no wiring short is found, have a mechanic verify the ECM's behavior on the CKP circuit with a scope. In very rare cases, the ECM's pull-up resistor circuit can fail and apply too much voltage. This requires dealer-level diagnosis.

Always exhaust sensor and wiring possibilities before suspecting the ECM.

When to Call a Professional

A short to voltage in the CKP sensor circuit can damage the ECM if not addressed. Have this diagnosed by a mechanic familiar with your vehicle's wiring before the ECM sustains further damage. A mechanic with a wiring diagram can trace the short efficiently. Expect $100-$200 for diagnosis and $100-$300 for the sensor and wiring repair.

Frequently Asked Questions

What is the crankshaft position sensor and why is it so important?

The crankshaft position sensor monitors the spinning crankshaft at the bottom of the engine. It counts the teeth on a toothed wheel (reluctor ring) as they pass by the sensor. This tells the ECM exactly how fast the engine is spinning (RPM) and where each piston is in its cycle. The ECM uses this data to time every spark plug firing and every fuel injector pulse. Without it, the engine simply won't run correctly — or at all.

Can P0338 cause my car to stall while driving?

Yes — a high voltage reading on the CKP circuit can cause sudden stalling. The ECM may interpret the bad signal as an engine speed or timing error and cut fuel and spark to protect the engine. This can happen at any speed, including highway driving. If your car stalls unexpectedly and P0338 is stored, treat this as an urgent repair.

Can I damage my ECM by driving with P0338?

Potentially, yes. A persistent short to voltage on a sensor input can stress the ECM input circuit over time. While modern ECMs have some protection, prolonged exposure to incorrect voltages can cause damage. This is one reason to address P0338 promptly rather than letting it sit for weeks.