P0340 P0xxx · Powertrain (P) Medium severity
Camshaft Position Sensor Circuit Malfunction
No usable cam signal. Most engines will still start using the crank signal alone, but with sequential injection and VVT disabled.
Severity guidance: Medium — drivability or emissions affected, book it in this week
Symptoms you will notice
- Longer crank before starting
- Rough running
- VVT disabled
- Possible stalling
Common causes
Ordered from most to least likely — start at the top.
- 1 Failed camshaft position sensor
- 2 Open or shorted wiring
- 3 Damaged reluctor or trigger wheel
- 4 Oil ingress into the connector
How to diagnose it
Cheapest and least invasive first — most of these codes are not a parts problem.
- ✓ Compare cam and crank signals on a scope — they must stay in a fixed relationship.
- ✓ Check for oil inside the connector, a common failure mode.
- ✓ Measure sensor supply, earth and signal at the connector.
- ✓ Inspect the trigger wheel through the sensor bore if accessible.
Repair options
- Replace the camshaft position sensor
- Repair the wiring
- Clean the oil-contaminated connector
P0340 — frequently asked questions
Will the engine start without it? +
Usually yes, after a longer crank — the ECU falls back to crank-only synchronisation.
Is it sensor or timing chain? +
Scope both signals. If the relationship drifts, suspect the chain; if the cam signal is simply absent, it is the sensor or wiring.
Confirm the diagnosis before you buy parts
Send us the code, freeze-frame data and the vehicle — our engineers will tell you what to test first.