What does OBD code P0340 mean?
P0340 means the ECU is not receiving a valid signal from the camshaft position sensor (CMP sensor). The CMP sensor tells the ECU where the camshaft is in its rotation so fuel injection and ignition timing can be synchronised. Symptoms include engine management light, hard starting or no-start, rough idle, misfires, and stalling. In some cases the car will refuse to start at all. This code should be diagnosed promptly as it can leave you stranded.
Likely causes
Failed camshaft position sensor
The sensor itself has failed — most common cause; relatively inexpensive to replace
Wiring or connector fault
Broken, corroded, or chafed wiring between sensor and ECU causes intermittent or permanent loss of signal
Timing chain stretch or jump
If the timing chain has stretched, the cam sensor signal is present but out of phase — more serious
Reluctor ring damage
The toothed ring on the camshaft that the sensor reads can become damaged or dirty
ECU fault
Rare — ECU input circuit failure; only suspect after other causes are ruled out
Repairs you may need
Typical cost range: £80–£400 — CMP sensor: £80–200 fitted. Wiring repair: £60–150. Timing chain if required: £500–1,200+.
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