P0338 on the 6.7L Power Stroke is a crankshaft position sensor A circuit high input fault. The crankshaft position sensor tells the PCM the crankshaft's speed and position, which is the foundation for injection and timing. P0338 sets when the PCM reads the crank sensor signal too high or with too many pulses, indicating a wiring problem, electrical interference, or a sensor that is not producing a clean signal.
The crankshaft position signal is essential; without a trustworthy one, the engine cannot run or may stall. P0338 usually points to the sensor, its wiring, or the connector rather than the crankshaft itself. Because the signal is sensitive to interference and air gap, careful inspection of the sensor's mounting, wiring routing, and connector often reveals the cause before the sensor is replaced.
What P0338 means
The crankshaft position sensor generates a signal as the reluctor wheel passes it. P0338 sets when that signal reads high or shows more pulses than expected, indicating a short to voltage, electrical noise, an incorrect air gap, or a sensor producing an erratic signal. The PCM cannot rely on the crank signal, which affects timing and can cause stalling.
Common causes
- Crank sensor signal wire shorted to voltage
- Electrical interference or a damaged shield
- Corroded or loose sensor connector
- Incorrect sensor air gap or debris on the reluctor
- Failed crankshaft position sensor
Symptoms
- Hard starting, stalling, or a no-start
- Rough running or intermittent cutting out
- Check engine light with P0338 stored
- Erratic tachometer behavior
- Hesitation or surging under load
How to diagnose it
Inspect the crank sensor connector for corrosion, moisture, and a secure fit, and back-probe to check the reference and ground. Examine the signal wiring for a short to voltage and for routing near sources of electrical noise. Confirm the sensor is mounted correctly and that the reluctor wheel is clean and undamaged. Watch the RPM signal with a scan tool while cranking and running to catch dropouts or noise. Compare against the camshaft signal for correlation.
How to fix it
Repair a signal wire shorted to voltage and address any source of interference, then clean or replace a corroded connector. Correct the sensor mounting or air gap and clean any debris from the reluctor. If the wiring and mounting are good but the signal is erratic, replace the crankshaft position sensor. After the repair, clear the code, confirm a stable RPM signal while cranking and running, and road test. For crankshaft position sensors and connectors for your 6.7L Power Stroke, contact sales@coredieselparts.com.
Frequently asked questions
Can P0338 cause a no-start?
Yes. The PCM needs a clean crank signal to fire the injectors. If the signal is unreliable, the engine may crank without starting or stall after starting.
What is the difference between P0337 and P0338?
P0337 is the crank sensor circuit reading low and P0338 is the same circuit reading high or noisy. Both point at the sensor, its wiring, and the connector from opposite electrical directions.
Is P0338 the sensor or the wiring?
Both are possible. Check for a short to voltage and electrical noise, confirm the connector and mounting, and replace the sensor only if the signal stays erratic with good wiring.
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