P0335 — Crankshaft Position Sensor A Circuit Malfunction — LB7 Duramax
Diagnostic reference for LB7 Duramax (2001–2004) P0335.
What it means
The engine control module has detected an electrical or signal fault in the crankshaft position sensor circuit.1
Most likely causes
- Crankshaft position sensor A circuit electrical fault — ECM sees an electrical or signal fault in the crankshaft position sensor circuit.1
- Wiring/connector issue to crankshaft position sensor — Open, short, or high resistance in the sensor harness or connector can set the circuit malfunction.1
- 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
- Verify code P0335 is present and review freeze-frame data.
- Inspect crankshaft position sensor connector and wiring for damage, corrosion, or loose terminals.
- Check sensor supply/reference voltage and signal circuit continuity per service information; compare to expected values.
- Inspect crankshaft position sensor mounting and air gap; look for contamination or damage to sensor tip.
- Clear codes, road test, and confirm if P0335 returns.
- If circuit tests normal, evaluate ECM inputs for crank sensor signal integrity.
- Document findings and retain freeze-frame for intermittent faults.
Parts and tools you may need
- Digital multimeter
- Scan tool with live data
- Wiring diagram for LB7
- Basic hand tools for sensor access
Tools you’ll need
- digital multimeter — Checks sensor supply/reference voltage and signal circuit continuity per service information for the crankshaft position sensor circuit.
- OBD-II scan tool — Verifies P0335 is present, reviews freeze-frame data, and confirms code return after road test.
- inspection mirror — Allows visual inspection of the crankshaft position sensor mounting, air gap, and sensor tip for contamination or damage in tight engine locations.
- terminal test kit — Tests connector terminals for damage, corrosion, or loose fit in the crankshaft position sensor wiring harness.
Rough cost and difficulty
| Likely repair | Parts | Shop labor | Who usually does it |
|---|---|---|---|
| ECM/PCM software update | — | 0.5–1.5 hrs | Shop |
| Wiring or connector repair | $10–$100 | 1–4 hrs | DIY with tools and a manual |
| Crankshaft or camshaft position sensor | $40–$200 | 0.5–2 hrs | DIY with tools and a manual |
| ECM/PCM replacement (programmed) | $600–$2,000 | 1–3 hrs | Shop |
Typical US independent-shop figures; labor runs about $120–$180 per hour (dealers charge more). Confirm the diagnosis before buying parts.
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.
Check for recalls
Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.
Sources
Repair videos: P0335 on the LB7 Duramax
Third-party videos, not ours — picked for this engine. Confirm anything against the factory service information for your truck.
Spotted an error, or something missing? Tell us
Run a LB7 Duramax? This goes straight to the editor — it is not published.