P0340

What the Code Means

P0340 points to a fault in the camshaft position sensor circuit. The sensor tracks camshaft position relative to the crankshaft so the DME can maintain correct valve timing.

When the sensor fails or its circuit is damaged, the control unit loses synchronization between the shafts, and the engine can stall at random. Typical causes: a failed sensor, wiring problems, or a damaged trigger wheel.

Symptoms

• Random engine stalls, including sudden ones — the DME loses shaft position synchronization
• Rough idle
• Hard starting (long crank)
• Check Engine light on

Diagnosis and Repair

1. Read fault codes with an ISTA or OBD2 scanner and note any related errors.
2. Check the camshaft position sensor wiring and connector: damaged insulation, corroded contacts, a loose connector.
3. Inspect the trigger wheel — damage there produces a bad signal even with a good sensor.
4. If the fault is confirmed, replace the camshaft position sensors with BMW OEM parts: intake 11361433772 and exhaust 11361433773.
5. When replacing the sensors, fit new O-rings 11361433774.
6. Clear the fault codes and take a test drive to confirm the error doesn't return.

The classic diagnostic mistake is replacing the sensor without checking the wiring and connector: an open or corroded circuit sets the same code with a perfectly good sensor.

Secondary Damage

• Frequent engine stalls while driving create unsafe conditions — risk of losing control and losing brake booster assist with the engine off.
• Prolonged misfires send unburned fuel into the exhaust and damage the catalytic converter.
• In rare cases, a complete sensor failure can lead to timing chain problems.

Don't put off the repair: beyond driving safety, a failed catalytic converter is an expensive consequence you can avoid with a timely sensor replacement.