Possible causes

– Faulty Camshaft Position Sensor
– Camshaft Position Sensor harness is open or shorted
– Camshaft Position Sensor circuit poor electrical connection
– Faulty Engine Control Module (ECM)

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.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Lack/Loss of Power
– Engine Stall

P0391 HYUNDAI Description

The Camshaft Position Sensor (CMPS) is a sensor that detects the compression Top Dead Center (TDC) of the NO. 1 cylinder. The CMPS consists of a hall type sensor and a target on the end of the intake camshaft. When the target triggers the sensor, the sensor voltage is 5V. If not, the sensor voltage is 0V. These CMPS signal is sent to the Engine Control Module (ECM) and the ECM uses the CMPS signal for synchronizing the firing of sequential fuel injectors.