Diesel Trouble Codes

P0335 — Crankshaft Position Sensor A Circuit Malfunction (LB7 Duramax)

Diagnostic reference for LB7 Duramax (2001–2004) P0335.

Updated September 2, 2026

What it means

The engine control module has detected an electrical or signal fault in the crankshaft position sensor circuit.1

Most likely causes

  1. Crankshaft position sensor A circuit electrical fault — ECM sees an electrical or signal fault in the crankshaft position sensor circuit.1
  2. Wiring/connector issue to crankshaft position sensor — Open, short, or high resistance in the sensor harness or connector can set the circuit malfunction.1
  3. ECM signal processing fault — ECM detection of abnormal crank sensor signal as defined by SAE J2012 generic OBD-II / GM enhanced.1

How to diagnose

  1. Verify code P0335 is present and review freeze-frame data.
  2. Inspect crankshaft position sensor connector and wiring for damage, corrosion, or loose terminals.
  3. Check sensor supply/reference voltage and signal circuit continuity per service information; compare to expected values.
  4. Inspect crankshaft position sensor mounting and air gap; look for contamination or damage to sensor tip.
  5. Clear codes, road test, and confirm if P0335 returns.
  6. If circuit tests normal, evaluate ECM inputs for crank sensor signal integrity.
  7. Document findings and retain freeze-frame for intermittent faults.

Parts and tools you may need

Rough cost and difficulty

Parts and labor vary by region and shop; obtain local estimate.

When to see a pro

If diagnosis points to ECM internal fault, high-pressure fuel system work, or requires removal of safety-critical components, have a qualified diesel technician perform the work. Do not attempt repairs to high-pressure fuel lines or other safety-critical systems without proper training and equipment.

Sources

  1. Curated DTC seed — LB7 Duramax (curated) ↩︎ ↩︎ ↩︎ ↩︎