What does P0340 mean?
Camshaft Position Sensor "A" Circuit (Bank 1)
Direct Answer
P0340 means the ECM is not receiving a valid signal from the Bank 1 camshaft position sensor. The cam sensor works together with the crankshaft sensor to precisely time fuel injection and ignition. A failed cam sensor can cause hard starting, stalling, and misfires.
Common Symptoms
- ✓Check engine light on
- ✓Hard starting (may crank long before firing)
- ✓Engine stalling
- ✓Rough idle
- ✓Misfires
- ✓Poor acceleration
Common Causes
- 01Failed camshaft position sensor
- 02Damaged sensor wiring or connector
- 03Reluctor wheel damage on camshaft
- 04Timing chain wear causing out-of-range cam position (also sets P0016)
How to Fix P0340
Inspect wiring and connector
Check for damaged insulation, corrosion, and loose connections at the cam sensor connector.
Test sensor output
Using an oscilloscope or scan tool live data, verify the sensor produces a clean square wave signal while cranking. A missing or erratic signal confirms sensor failure.
Replace the camshaft position sensor
These sensors are relatively inexpensive and straightforward to replace on most engines.
Frequently Asked Questions
Is the cam sensor the same as the crank sensor?
No. They are separate sensors. The crankshaft position sensor (P0335) monitors the crankshaft. The camshaft position sensor (P0340) monitors the camshaft(s). Both signals are needed for precise fuel and ignition timing.
Estimated Repair Cost
$60–$400
Sensor: $20–$100. Labor: $50–$300.
Safe to Drive?
No — avoid driving
Limit driving — the engine may stall unexpectedly.
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