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P0391 - Camshaft Position Sensor 'B' Circuit Range/Performance Bank 2

Possible causes
- Faulty Camshaft Position Sensor
- Camshaft Position Sensor harness is open or shorted
- Camshaft Position Sensor circuit poor electrical connection
- Faulty starter motor
- Starting system circuit
- Dead (Weak) battery
Tech notes
Sometimes and in some models, low battery voltage or a weak starter can can trigger a Camshaft Position Sensor code.
When is the code detected?
The camshaft position sensor signal sent to the Engine Control Module (ECM) during the first few seconds of engine cranking is out of range.
Possible symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Lack/Loss of Power
- Engine Stall
P0391 Description

The Camshaft Position Sensor is an electronic device used in an engine to record the rate at which the camshaft is spinning. This information is used by the Engine Control Module (ECM) to control ignition and fuel injection. The camshaft position sensor senses the retraction of camshaft (intake) to identify a particular cylinder. The camshaft position sensor senses the piston position. The sensor system consists of a rotating part, typically a disc, as well as a static part, the actual sensor.

When the engine is running, the high and low parts of the teeth cause the gap with the sensor to change. The changing gap causes the magnetic field near the sensor to change. The change in the magnetic field cause the voltage from the sensor to change.

When the crankshaft position sensor (POS) system becomes inoperative, the camshaft position sensor provides various controls of engine parts instead, utilizing timing of cylinder identification signals.

P0391 Information for specific makes
P0391 AUDI Camshaft Position Sensor 'B' Circuit Range/Performance Bank 2
P0391 HYUNDAI Camshaft Position Sensor 'B' Circuit Range/Performance Bank 2
P0391 KIA Camshaft Position Sensor 'B' Circuit Range/Performance Bank 2
P0391 VOLKSWAGEN Camshaft Position Sensor 'B' Circuit Range/Performance Bank 2
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