My ram 1500 5.2 motor give a code p1391 what is

P1391 - Intermittent loss of CMP or CKP.

Generally, this code will indicate that the crankshaft sensor is faulty. The sensor is mounted in a fixed position in the engine block. The tip of the sensor protrudes into the crankcase at a distance of 0.05 plus or minus 0.02 inch from the crankshaft. I would check the wiring harness for loose connections. Inspect the trigger wheel behind the crankshaft pulley and the sensor for damage. replace if needed.


If a crank or cam sensor fails, the engine will not start. both of these sensor circuits can be checked with a voltmeter or lab scope.If the sensors are receiving the correct amount of voltage and have good low-resistance ground circuits, their output should be a pulsing digital signal or voltmeter reading while the engine is cranking.

If any of these conditions do not exist, the circuit needs to be repaired or the sensor needs to be replaced. The location of the Cam shaft sensor will be mounted on the distributor. Use the sensors terminals for testing. Over 7 volts is ok, but anything below that at the sensor will indicate that the sensor wires are bad. If the voltage is low at the PCM, the PCM is suspect.