P0340 — Camshaft position sensor (CMP) circuit

What this code generally means, its most common causes, and how serious it is.

TYPE: GENERICSYSTEM: ENGINE SENSORS

What does the code P0340 mean?

The camshaft position sensor (CMP) confirms to the control module which cylinder is on its intake or exhaust stroke, helping precisely time fuel injection — especially on direct-injection engines or those with variable valve timing.

Common possible causes

A failing CMP sensor — the most common cause.
Damaged wiring or connector — exposed to engine heat.
Timing chain or belt wear — can desynchronize the signal even with a healthy sensor.

General severity

Moderate to serious — worth a prompt check

The effect varies by vehicle: some engines run nearly normally thanks to the crankshaft sensor as a backup, others start hard or idle roughly. Worth checking promptly rather than guessing.

This is still a general severity for this code, not a diagnostic for your car. Only a real read of your codes, with your mileage and vehicle history, can tell what's really going on.

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Meca doesn't replace an in-person check by a professional. For any serious sign (a flashing light, a major loss of power, a fuel smell), see a mechanic promptly.

Frequently asked questions

Is this as urgent as the crankshaft sensor code (P0335)?

Generally a bit less, since many control modules can keep the engine running using just the crankshaft signal — but it's still worth checking promptly, not ignoring.

Is this related to the timing chain?

It can be: a worn chain or belt can desynchronize the sensor's signal even if the sensor itself is fine.

My car is hard to start — is that related?

That's a possible symptom, particularly on engines that rely heavily on this signal for direct injection.