P0340 fault code: camshaft sensor circuit fault
Plain-language definition
Camshaft Position Sensor A Circuit Bank 1 or Single Sensor
What does it mean?
The camshaft position sensor (cam sensor for short) tells the engine computer the position of the camshaft. By using this signal together with the crank sensor's signal, the engine computer can tell which cylinder is on its compression stroke; that way it delivers fuel and, on petrol engines, ignition to the right cylinder at the right moment. On engines with variable valve timing, the camshaft's position is also monitored with this sensor.
The code's generic definition covers sensor "A" on Bank 1, or the only camshaft sensor if the engine has just one; on most engines "A" is the sensor for the intake camshaft. While the engine is turning, the engine computer expects a signal from this sensor in a set pattern. If the signal never arrives, drops out now and then, or an electrical problem shows up in the circuit, it stores P0340.
You may notice the engine being slow or hard to start, needing to crank it for a long time, rough idling, misfiring and a loss of power. On some engines the engine computer can still run the engine without this signal, but performance drops; on others the engine may not start at all.
How serious is it?
This is a Priority code: if the engine computer can't reliably tell the cylinders' timing apart, the engine may be hard to start, misfire or not start at all. Even if the symptoms come and go, it's a good idea not to delay having it checked.
Severity is a guide; if the warning light is flashing or you notice symptoms while driving, have the car checked at a workshop.
Common general causes
- A failed cam sensor
- A break, corrosion or chafing at the sensor's connector or in its wiring
- Oil leaking into the sensor's connector, or the sensor fouled with oil and metal dust
- Damage to the trigger wheel the sensor reads (the toothed wheel or vane on the camshaft)
- Less often, a fault in the engine computer
The list shows general causes; a workshop finds the actual cause on your car with a check.
Definitions by make
Some manufacturers record the same code under their own wording:
- Fiat
- signal phase motor,
- Honda
- Camshaft Position (CMP) Sensor No Signal
Related codes
How does it appear in the 2dakika report?
Camshaft Position Sensor A Circuit Bank 1 or Single Sensor
If the code is read as a confirmed (stored) fault, the report shows it with the "Priority" severity; in pending or past records, codes that don't request the warning light and aren't critical appear as "Info". If the engine computer stored them, the conditions when the fault was recorded (engine temperature, rpm, speed) are shown too.
Read this code with the OBD-X1, and clear it from the app after the repair.
Clearing the code doesn't fix the fault; if the problem persists, the code comes back.