P0340 on GMC: How to Diagnose & Fix
Camshaft Position Sensor Circuit Malfunction
1 GMC model · 1 documented issue · 1 critical · $80-$300 repair
P0340 on GMC by model: symptoms, diagnosis and fix
The 4.2L LL8 inline-6 engine in the 2002-2009 GMC Envoy is notorious for crankshaft position sensor failures that cause intermittent stalling and no-start conditions. The sensor is located on the side of the engine block and is exposed to heat soak from the exhaust manifold, accelerating its failure. A failing sensor causes the PCM to lose track of crank position, resulting in the engine cutting out without warning — often at highway speed. The issue tends to be intermittent at first, making diagnosis challenging. Replacement is straightforward and the part is inexpensive.
Common Symptoms
- Engine stalls without warning at any speed
- Hard start or no-start after hot soak
- Check engine light with code P0335 or P0336
- Engine cranks but won't fire when hot
- Intermittent stall that restarts after cooling down
- Rough idle followed by stall
How to Fix
Replace crankshaft position sensor (ACDelco 213-3521 or Delphi SS11378). Clear codes and test. If stalling continues, inspect camshaft position sensor (ACDelco 213-3522) as secondary cause. Verify PCM software is current — older PCM calibrations make the engine overly sensitive to sensor signal dropout.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Engine Crankshaft Position SensorCross-ref235-1078
Fitment confirmed against the ShowMeTheParts catalog for this vehicle's year and engine.
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Sources for this issue (1)
P0340 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0340 mean on a GMC?
P0340 stands for "Camshaft Position Sensor Circuit Malfunction." This code means the engine computer lost or received an erratic signal from the camshaft position sensor. That sensor tells the computer the exact position and speed of the camshaft, which it uses together with the crankshaft sensor to time fuel injection and spark precisely. When the camshaft signal is missing, intermittent, or out of range, the computer sets P0340. Symptoms often include hard starting, stalling, rough running, or a no-start because the engine can't time itself correctly. On GMC it is documented across 1 model: Envoy.
What are the most common causes of P0340?
The most common causes of P0340 are: Failed camshaft position sensor, Corroded or loose sensor connector, Damaged or shorted sensor wiring, Bad reluctor/tone ring on the camshaft, Loose timing chain/belt or jumped timing, Metal debris or oil contamination on the sensor tip, Poor sensor power or ground supply, Faulty PCM/ECM (rare). The specific cause varies by vehicle.
How much does it cost to fix P0340 on a GMC?
Published repair estimates on GMC range from $80 to $300 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0340 on a different make?
View P0340 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.