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P0340 P0xxx · 动力总成（P） 中严重度
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.
严重程度说明： 中——已影响行驶或排放，请本周内安排检修
你会注意到的故障现象
- Longer crank before starting
- Rough running
- VVT disabled
- Possible stalling
常见原因
按可能性从高到低排列——从最上面开始查。
- 1 Failed camshaft position sensor
- 2 Open or shorted wiring
- 3 Damaged reluctor or trigger wheel
- 4 Oil ingress into the connector
如何排查
先做花钱最少、侵入最小的检查——大多数这类码不是零件问题。
- ✓ 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.
维修方案
- Replace the camshaft position sensor
- Repair the wiring
- Clean the oil-contaminated connector
P0340 —— 常见问题
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.