P0340 Camshaft Position Sensor A Circuit Bank 1 or Single Sensor

Investigate soon

The ECU has logged a fault on P0340. The definition below is the exact wording the standard uses for this code.

Can you drive it? The engine light will stay on and the car may run in a reduced-power mode. Read the freeze-frame data to see the conditions the fault was logged under.

The definition

P0340: Camshaft Position Sensor A Circuit Bank 1 or Single Sensor.

P0340 is a powertrain code (the engine or gearbox), defined by the SAE standard - it means the same thing on any make of car, and any generic OBD-II reader will decode it.

What to check first

Cheapest and fastest checks first:

Check the oil level and when it was last changed. These adjusters run on oil pressure and are the first thing to suffer from old or low oil.
Check the cam adjuster solenoid and its screen for sludge.
Only then suspect the timing chain or belt and its tensioner.

What actually causes this on a VAG

The camshaft position sensor is a small Hall sensor at the end of the cylinder head that watches a ring or tooth on the camshaft, so the ECU knows which stroke each cylinder is on. On VAG scan tools it's often labelled G40. On many engines the ECU can still work out what it needs from the crankshaft sensor, which is why the classic symptom is long cranking before it fires - or an occasional hot no-start - rather than a car that's dead on the drive; some engines are less forgiving and won't start at all. "Circuit bank 1" means the ECU isn't getting a usable signal from that sensor.

Most likely causes, in order

Oil or corrosion in the sensor's connector. When the sensor's seal starts to weep, engine oil wicks up inside the wires and into the plug, and the contacts stop making cleanly. Unplug it and look for oil, green corrosion or spread pins - a common and cheap finding on these engines, and the first thing to rule out.
The sensor itself has failed. Hall sensors commonly fail with heat, so the classic pattern is a car that starts fine cold and cranks and cranks once it's hot. If the wiring and plug are clean and the fault follows temperature, the sensor is the likely culprit.
Wiring damage or a lost supply/earth. Check the loom where it passes near the cam cover, coils or a bracket for chafing. If other sensors have thrown codes at the same time, look at the shared supply and earth rather than the individual sensor.
A cheap replacement sensor. If a cam sensor was fitted recently and the code has returned, the part is a fair suspect. Aftermarket cam sensors have a poor reputation for early failure, so a genuine or reputable OE-supplier part is worth the extra.

Worth knowing: On many VAG engines the ECU can keep things running on the crankshaft sensor alone, so a P0340 sitting alongside a complete no-start deserves a second look rather than an assumption - check for crankshaft sensor codes and wiring faults too. Read all the stored codes before you buy anything.

Reading the code is the easy part

A code names the circuit that complained. What tells you why is watching the sensor behind it while the engine runs — and that is where a code reader stops and a diagnostic tool starts.

VAGPULSE reads every module in a VW, Audi, Skoda or SEAT — not just the engine — shows the live measuring blocks behind this fault, gives you the freeze-frame conditions it was logged under, and clears it once you have fixed it. It also does what a generic OBD reader cannot on a VAG: service resets, coding, adaptations, and Stage 1–3 flashing with your original file saved first.

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Common questions

What does P0340 mean?

P0340 means Camshaft Position Sensor A Circuit Bank 1 or Single Sensor. It is logged when the ECU sees this circuit outside its expected operating window.

Can I drive with P0340?

The engine light will stay on and the car may run in a reduced-power mode. Read the freeze-frame data to see the conditions the fault was logged under.