P0340: Camshaft Position Sensor Circuit Malfunction

What does P0340 mean?

What are the symptoms of P0340?

What causes P0340?

• Failed camshaft position sensor, an internal circuit or Hall-effect element fault that stops it sending a clean signal

  : high

• Damaged or corroded wiring and connector at the CMP sensor, often from heat, vibration, or moisture breaking the circuit

  : high

• Oil contamination on the sensor tip or connector, usually from a leaking valve cover or timing cover gasket, which masks the magnetic signal

  : medium

• Sheared, worn, or debris-covered reluctor (tone) ring on the camshaft, so the sensor cannot read teeth correctly

  : medium

• Excessive sensor air gap from a loose or shifted sensor, weakening the signal the ECU reads

  : low

• Timing chain stretch shifting cam timing and producing an erratic CMP signal, often logged together with P0016

  : low

Is it safe to drive with P0340?

How do you diagnose P0340?

How much does P0340 cost to fix?

P0340 on specific vehicles

Related diagnostic codes

• P0341
• P0342
• P0343
• P0345
• P0016

Common questions about P0340

What does code P0340 mean?

P0340 is the Camshaft Position Sensor Circuit Malfunction code. It means the engine computer is not receiving a usable signal from the camshaft position sensor. The ECU uses that signal to know where the camshaft is and to time fuel injection and ignition, so a lost or erratic signal directly affects whether the engine starts and runs.

What are the symptoms of P0340?

The most common signs are hard starting or a no-start where the engine cranks but will not fire, sudden stalling, rough idle, hesitation, and loss of power. The check engine light is on, and some vehicles drop into reduced-power limp mode. Symptoms can be intermittent, coming and going as the sensor or its wiring fails.

What causes a P0340 code?

By far the most common cause is a failed camshaft position sensor. After that comes damaged or corroded wiring and connectors, oil contamination on the sensor from a leaking valve cover or timing cover gasket, and a worn or damaged reluctor (tone) ring on the camshaft. Less often it is timing chain stretch shifting the cam timing, which usually also sets P0016.

Is it safe to drive with a P0340 code?

Not really. If the engine starts and runs you can drive a short distance to a shop, but an intermittently failing CMP sensor can stall the engine without warning, which is dangerous in traffic. If the car stalls unpredictably or will not restart, do not drive it, have it towed.

How do you fix and clear a P0340 code?

In most cases the fix is replacing the camshaft position sensor, then clearing the code with a scan tool and confirming it does not return on a test drive. First check and repair any oil-soaked connector or damaged wiring, since a fresh sensor will not cure a wiring fault. If the sensor and wiring are good, the reluctor ring and timing chain need inspection before the code will clear for good.

How much does it cost to fix P0340, and does bank 1 versus bank 2 matter?

A camshaft position sensor replacement typically costs about 40 to 180 euros including labour, with the sensor itself often 20 to 80 euros and labour 30 to 120 euros. P0340 refers to the bank 1 (or only) sensor on inline engines, while P0345 is the matching bank 2 sensor on V6 and V8 engines. On most cars the sensor is accessible on the cylinder head, so cost stays low; tucked-away locations on some turbo engines raise the labour.

Can P0340 cause a no-start?

Yes. Some ECUs need a valid camshaft signal before they will fire the injectors, so the engine cranks and never starts. Others fall back on the crankshaft signal alone, in which case it starts and runs, but with reduced performance and the warning light on. Which behaviour you get depends on the engine management, not on how bad the sensor is.

Can I replace the camshaft position sensor myself?

On most engines, yes. It is usually one bolt and one connector, and 15 to 30 minutes of work. The hard part is finding it: it sits near the camshaft at the top or the front of the engine, and on some V-engines the rear bank sensor is buried. Look up the location for your specific engine before you start.

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