Jethro4days

Hello everyone. I was on my way home from work. (Highway) and my check engine came on. I pulled off the nearest exit into a gas station and popped the hood. Couldn't see anything out of the ordinary. The jeep was running fine as far as I could tell. So tighten the gas cap, closed the hood and finished my commute which was about 35 miles. I stopped at auto zone to have them pull the codes and it listed two. P0340 and P1391
P0340 - probable cause 1. Cam sensor defective 2.check connector and wiring to sensor
3.engine mechanical condition timing belt/chain out of time.
P1391- probable cause 1. Timing belt or chain stretched or jumped 2. Defective CMP sensor
my vehicle is
99 Cherokee sport automatic 138k
Has anyone had to deal with this before? I've tried searching other threads but couldn't find much.
I have some questions. I've seen the word CPS used on here before but wasn't sure if it meant CAMshaft sensor or CRANKshaft. What is the difference between the 2? Where is the camshaft sensor located? Is it difficult to replace? I'm still very new to tinkering on my XJ so please bare with me. Is my jeep okay to drive? It's my daily driver and don't want to be stranded. And and all advice is greatly appreciated

CCKen

How's it running?

Jethro4days

It runs fine as far as I could tell. No stalling, sputtering or anything like that. I thought maybe a loss of power but I might have been physcing myself out

CCKen

If you had an actual Cam Sensor fault the engine would be running poorly.


Clear the code and inspect the wiring at and around the Cam Sensor and the Crankshaft Position Sensor for chafing.

Jethro4days

And by chafing you mean exposed and touching another part of the vehicle? Or rubbing against itself?. I will still obviously check for both.

CCKen

Yes.


Visual examination of wiring and connectors is always the first step in diagnosing electrical issues. In fact, wiggling the wire harnesses will, at times, reveal the bad spot(s) that cannot be seen.

ENV

Has anyone ever figured this out? I got a CEL on my way home from work today. I have a 2000 WJ Grand Cherokee with the 4.0. I checked the codes and got these exact 2 codes. One was pending the other was current code. Current code was the one for the Cam Position Sensor "A" circuit (Bank 1 or Single Sensor) P0340.

The issue is that I got home, shut the car down, went inside for a couple of hours, and when I came back out to go to the store the car cranked and cranked nice and strong but would not start at all.

Any ideas on the solution to this issue?

tjwalker

My experience when you see both of these codes together (P1391, P0340), is that it usually ends up being related to the camshaft position sensor "circuit". Remember that the word circuit includes not only the camshaft sensor, but the connectors, wiring and all the way back to the computer.

The cam sensor can be tested with a meter and a manual. I would start there.

Good luck and keep us updated!

97grand4.0

Agree with the above. Hallmark of failed cam sensor is it runs then wont start. However is also the hallmark of failing crank sensor. But if the codes point to cam sensor, get a junkyard one and toss it in to see if makes any difference.

briankiethmyers@gmail.com

Hey, try this. Get in your Jeep, turn key to run, then off then back on a total of 3 times. Look at your Odometer the current codes will display one by one. At the end it will say “ done or complete or none follow or something to let you know that’s it”. BTW this works on a lot of Chrysler products and even some other year, make, model cars.