I have a 2001 Cherokee XJ 4.0L. When I bought the XJ it coded by scanner a P1391 and check engine light on. Since then, Ive had the CamPS and CrankPS replaced. Still a rough idle and the occasional dead at stop lights while in gear. Possible fuel pump issue? Just did that tonight. Started up clean and I let it idle for a few minutes. Seemed all tip top til I was about to take it for spin and it died. Rough idle then death. FRACK! Now it wont start and just cranks. It has gas. It was running okay before it died. Im at a loss. I tried the three turn of the key to attempt to find any codes. Nothing. I tried the diagnostic check of holding the odometer button down then turned the key just before ignition. Again, nothing. Please help! And yes. Ive looked all through this forum for answers before posting.

 

What is the voltage with a clamp on the starter where the wire from battery positive leads to a clamp on the nut at the block where the battery negative leads when cranking and when not cranking?

 

The brand of sensors could be an issue as well if they are not Mopar.

 

Thanks! After having my ride towed to my mechanic to check codes, even though I just replaced the CPS (with stupid after-market POS), it showed the same dreaded P1391 code.
He and I researched again and I just ordered a MOPAR CPS seeing how sensitive this part is. HOPEFULLY, this'll solve the issue once installed. MOPAR sensors from now on.

 

This IS odd. So replaced the CrankPS with a MOPAR cps. Starts right up. No cps code P1391. GREAT! Now to replace the CamshaftPS with MOPAR since after runner a scanner its listing a camshaft position sensor issue among others including possible PCM/ECU failure. ( WTF?!?!??!!?) Looking at the ecu, it's straight mounted to the sidewall, no protective cover and with four screws. HMMM?. So, unmounted the ecu, wrapped it in some simple heat resistant spongy fabric and set it next to the airbox. Yes, Ghetto but the XJ runs great! Idles smooth. No codes and no issues. Doesnt die on me at a stop light. Again......WTF?!?!??!!? Questions are:
Is there supposed to be a cover?
Is there supposed to be a mounting plate?
Is the ecu grounding against the sidewall?
Im at a loss currently and tired of throwing parts ($$$$$) at questionable issues. I know its a 20 year old XJ.

 

No to the cover and no to the is it grounded to the firewall. Only mounted there. Agree Mopar only on those two sensors the jury has been in a long time on that, many a newbie has experienced what you went through. Anything else the magnets are not strong enough to produce the required signal Replace both the ckps and cps. Not to say you dont have a connection issue to the PCM (not ecu) or a bad pcm too. Drive it and see.

 

After A LOT of research on this forum, YouTube and the inet regarding the cam sensor, I had a theory that if not aligned correctly, it may cause some of the issues I was experiencing at idle. DUH!
Today I removed the ignition coil pack and cylinder one spark plug, got it to TDC, then checked the alignment of the cam position sensor and found it was off by by about; give or take 1/4 inch using a high tech tool known as a toothpick. LOL I then realigned the CPS matching the holes and bottoned everything back up including a new set of plugs.
I have to say, it ran so smooth and pick up was miles better. No CEL, no stalling, no rough idle. FINALLY!!! F-YEAH!
Now if I can just figure out how to get the oil dip stick tube out since I broke the dip stick handle off and the dip stick is still in the tube.
As the saying goes.... "Create a new problem by fixing an old one"

 

Get a wire that is stiff get it red hot push it slowly in to the plastic , when it is in about a 1/2 inch spay some cold water on it to cool it and the wire should stick to it , then slowly pull on the wire to remove the dip stick . hope this works for you like it did for me .

 

'Just yanked the whole tube out to be done with it. Thanks for yall's help.

 

Where's your transmission dipstick?

 

I pulled it out after breaking the oil dip stick. Wasn't gonna have TWO broken sticks.