P0340 on Chevrolet: How to Diagnose & Fix
Camshaft Position Sensor Circuit Malfunction
1 Chevrolet model · 1 documented issue · 1 critical · $800-$1,800 repair
P0340 on Chevrolet by model: symptoms, diagnosis and fix
The LT1 (and 1996 LT4) uses a front-of-engine 'Opti-Spark' optical distributor mounted low behind the water pump, driven off the camshaft. It is highly vulnerable to moisture, heat, and ozone. The 1992-1993 units were completely unvented and are notorious for internal condensation and corrosion of the optical sensor disc. The leading real-world cause of failure is a leaking water pump directly above it dripping coolant onto/into the unit, but ordinary humidity and age also kill them. It is one of the single most defining reliability weak points of the 1992-1996 C4.
Common Symptoms
- Intermittent misfire
- Rough running / stumbling
- Stalling
- No-start (especially after rain or high humidity)
- Misfire that worsens when engine/weather is damp
- Backfiring
How to Fix
Replace the Opti-Spark distributor (later vented-style unit is the upgrade for 92-93 cars; a vacuum-vented design arrived on 1995-1996 units). Because the water pump sits directly above it and is the most common contaminant source, the accepted practice is to replace the water pump at the same time ('while you're in there'), since the front cover/serpentine and much labor overlaps. Many owners also drill/tap the water pump weep hole and route a hose away from the distributor.
Sources for this issue (3)
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 Chevrolet?
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 Chevrolet it is documented across 1 model: Corvette.
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 Chevrolet?
Published repair estimates on Chevrolet range from $800 to $1,800 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.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.