Like the title says, the jeep is running fine. But my check engine light is staying on. I'm getting a error code of p1391, which is the cps. I can clear the code with a scan tool, but it comes right back. I swapped out the cps, and I'm still getting the same symptoms. No change. Any suggestions?

 

1391 is intermittent loss of the cmp or ckp. Camshaft or crankshaft. I would pull the plugs apart and clean them out and see what happens.

 

also dielectric grease would help if any thing dose good luck and keep us posted

 

Good advice here^^.

RCBRC= Refresh Connections Before Replacing Components.

 

Yes, very good advice and exactly how I would proceed.

As the 1391 can be caused by EITHER the cam or the crank sensor, start by getting a spray can of electrical contact cleaner and thoroughly spray the connectors, add a dab of dielectric grease and reconnect.

There are 2 connectors for the crank sensor. The one on the sensor itself and the other one is inside of the engine bay near the firewall / #6 injector; don't forget that one!

If it continues to trip for a 1391 after the above, I'd consider getting a new camshaft position sensor installed.

 

You guys are a wealth of knowledge. Just awesome. Okay, did some connector cleaning and lubing. Still same issue. I still need to do the connector by the firewall. But I have a new symptom to add; it wont start sometimes. I turn the key to the on position, the fuel pump runs, and then she just cranks. I get out my scan tool, clear the 1391 error, and she fires right up. Soon as I roll forward or backwards, the code trips again. Jeep keeps running fine, but the code is back. I am about to buy a camshaft position sensor, but I wanted to see what you guys thought with the new symptoms. Keep in mind that I changed out crank position sensor twice and the symptoms have not changed.

 

Clean the connector for the crank sensor by the firewall. The signal from the sensor has to go through that connector to get to the computer. If there is resistance because of debris in that connector, that could create an "intermittent" fail situation.

Gotta ask if this is an aftermarket or a Jeep crank sensor. And you changed it twice, but was that with the exact mfg. sensor?

Kind of a long shot and not saying that is your problem, but there are a lot of junk aftermarket crank sensors. A guy on Jeep Forum changed his 3 times before getting one from Jeep that resolved his issues. I buy a lot of aftermarket parts, but the crank sensor is one thing I buy only from Jeep.

 

Guilty as charged on the aftermarket cps. . I got them from Napa. But the symptoms do not change regardless of the original or the aftermarket part being in there. So I have a feeling it is not the part. I am cleaning the connector today, and also I am checking on camshaft sensor.

 

How do you check the code without a scanner?

 

Update:
Last night I flashed the pcm in the jeep. I figured before I bought the camshaft position sensor I should try everything I could. I cleaned out the connector on the crankshaft sensor by the #6 injector, and the connector for the camshaft sensor. I also put dielectric grease in the contacts.

I had a slight leak on the water pump gasket, so for giggles I also replaced my water pump last night. And changed the oil and filter.

After all this, and flashing the pcm, I still had the 1391 error code. So I figured "fine, I'll buy the camshaft sensor". This morning I went to Napa, ordered the sensor and paid for it. $55. I walked out of the store, turned on the jeep, and the check engine light went out. Shut it off and restarted 15 times. Still no code. Drove it all morning till 1pm when I picked up the sensor that came in. Still no check engine or error codes. I scanned it, nothing. She is even running properly now as far as the fuel-air mixture is concerned (was a little rich before).

I kept the sensor and put it in the back of the jeep in my toolbox. I think this thing is F-ing with me. Either way, this has been a fun learning experience. Thank you TJ for your advice. Helped.

 

My favorite mantra: RCBRC=Refresh Connections Before Replacing Components.

 

Well, it decided to come back. The error code that is. So tonight I swapped out the camshaft sensor for the new one. Cranked her up and no more code. But yes, you are definitely right about refreshing connections. Last month had a slight issue with my fuel pump working intermittently, and I checked the connection. Whole bunch of dried up mud was in the connector. Soon as got it all out the fuel pump went back to normal.

 

I also have the p1391 code. In addition the p0351 (ignition coil #1 Primary Circuit -peak primary circuit current not achieved with maximum dwell time) and p0320 (no crank reference signal at PCM - no crank reference signal detected during engine cranking). On p1391 it seems from the forum to refresh all connectors and replace camshaft and crank shaft position sensors. Any advise on how to move forward on the other two codes?

 

Best to start a new thread as your question is about different codes. You'll get more accurate replies that way and is less confusing for the original poster.