I just bought this 5.9 magnum v8 a week ago and it’s got a check engine light. I just took my scanner to it and it gave me this code p1391. It’s also misfiring in cylinder 1. What’s going on I can’t seem to find anything online. My dad is pretty sure it’s a vacuum leak but I don’t know.
would you recommend changing out the crankshaft sensor? And I’ve been trying to research the location of the camshaft sensor and I can’t find anything could I get some insight to where I’m supposed to look

 

P1391 Intermittent Loss of CMP or CKP
Loss of crank or cam sensor. Crank sensors go more frequently than the cam sensors.

 

I just installed a new crank sensor and it’s still having issues. Misfiring in cylinder 1 too

 

What brand crank sensor? These trucks really don't like the aftermarket sensors......

 

just one I picked up from my local auto parts store I can’t exactly remember the brand

 

Probably duralast. But, if you changed the sensor, and are still having the same issue, pretty safe bet that its not the sensor......

 

Could be the cam sensor, Code is for both. If you had a high end scanner you could see on the scope witch one has the issue. Have you checked the cap/rotor, plugs and wires. Since you just got it you don't know the previous owner did.

 

I thought p1391 code was a 02 sensor problem ?

 

Nope. Intermittent cam/crank sensor.

 

Maybe somebody should make up a (updated)list of the PO codes and post it in the sticky's. I searched and see we have a diesel thread with them and these below but the 1391 is not there along with others(did i miss any?). Threads are closed so you can't update any missing codes. I have word document that has most of them but it's not helping any of the users here.
https://dodgeforum.com/forum/general-tech/15042-service-engine-codes-for-obd-ii-engines.html

https://dodgeforum.com/forum/general...d-engines.html

https://dodgeforum.com/forum/1st-gen...d-1-codes.html