P0340
P0340 Check Engine Code
Camshaft Position Sensor Circuit
The computer cannot see where the camshaft is in its rotation — no reliable camshaft position signal, or a circuit out of range. That is P0340. Some vehicles crank and will not start; others run poorly or stall when hot. Wiring at the connector, oil soaking the sensor, or a failed sensor are the usual suspects; timing belt or chain problems can also throw cam correlation off. Sorting signal loss from mechanical timing keeps you from replacing a sensor when the belt jumped.
Symptoms
- Check engine light with P0340 — may crank with no start on some models
- Stalling or hard restart when hot
- Rough running or reduced power
- Code after timing belt or chain service
- Oil leak soaking the cam sensor connector
Can I keep driving with a P0340 code?
If it starts and runs, drive carefully to diagnosis — stalling risk is real on some vehicles.
Crank no-start — do not keep cranking; tow or schedule mobile diagnosis.
Stalling in traffic — treat as urgent.
Common causes
- Failed camshaft position sensor
- Damaged wiring or connector at the sensor
- Oil contamination from a valve cover leak
- Timing belt or chain off one tooth (correlation codes may accompany)
- Aftermarket sensor with incorrect air gap
Often sounds like
- P0016 crank/cam correlation — timing mechanical issue
- Crank sensor codes — different circuit, similar no-start
If you wait
- Stranded no-start
- Stalling in traffic
- Timing damage if the belt jumped and only the sensor is replaced
How we check it
- 1 Oscilloscope or scan data for cam signal presence
- 2 Inspect connector and oil intrusion
- 3 Verify timing correlation when sensor and wiring look good
What happens next when you bring it in?
- 1 Call with whether it is a no-start, a stall, or just the light on.
- 2 We test the cam signal circuit and timing evidence before swapping the sensor.
Questions we get a lot
- What does P0340 mean?
- P0340 is Camshaft Position Sensor Circuit Malfunction. The engine computer did not receive a valid cam position signal from the sensor circuit.
- Will P0340 prevent my car from starting?
- On some models, yes — crank no-start until the cam signal is restored. On others it runs rough or stalls. Tow in if it will not start reliably.
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