P0340 on GMC
Camshaft Position Sensor Circuit Malfunction
P0340 on GMC vehicles indicates camshaft position sensor circuit malfunction. Au7o has documented this code across 1 GMC model — most commonly on Envoy. 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. Typical repair costs on GMC range from $80 to $300, depending on the specific model and root cause.
Common Causes of P0340
- •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)
P0340 on GMC by Model
GMC Envoy(1 issue)
- 4.2L I6 Crankshaft Position Sensor Failure and Stalling2002-2009
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.
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View P0340 across all makes →Frequently Asked Questions
What does P0340 mean on 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 specifically, this code is documented across 1 model.
What causes P0340 on GMC vehicles?▼
Common causes on GMC: 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. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0340 on a GMC?▼
Repair costs on GMC range from $80 to $300, depending on the specific model and root cause.
Which GMC models have P0340 documented?▼
Au7o has documented P0340 on 1 GMC model: Envoy.