JeffSmithart

1998 Jeep Cherokee 4.0 in-line 6

Just bought it and the engine light was on when I bought it. It runs great. no timing issues or anything.

Had it checked at auto zone and got these codes back.

Troubleshooting P1391
OEM Brand Crystler

Definition:
CMP or CKP signal intermittent condition
Explanation:
The ECM detected the actual CMP position disagreed with the expected CMP level
Probable Cause:
1. Timing Belt or chain stretched or jumped.
2. Defective CMP sensor


Troubleshooting P0320
OEM Brand Domestic

Definition:
Crank Sensor Condition
Explanation:
The crankshaft position sensor is monitored for errors
Probable Cause:
1. Crank Sensor Defective
2. Check Connector and wiring to sensor
3. check trigger wheel for damage


Troubleshooting P0340
OEM Brand Domestic

Definition:
Cam Sensor Condition
Explanation:
The camshaft position sensor is monitored for errors
Probable Cause:
1. Cam Sensor Defective
2. Check connector and wiring to sensor
3. Engine mechanical condition-timing belt/chain out of time.


As I said the thing runs smooth as silk. It's not out of time. The guy at Autozone said this jeep doesn't even have an Cam Sensor, though this obviously says it does. I have to fix the check engine light before I can get it inspected where I live. I have to have it inspected before I can get it registered.

Any help would be appreciated.

jeepxj99

there is a cam position sensor. it is located by removing the distributor cap and rotor button. the round piece with a wire harness under the rotor button is the sensor. it is also referred to as a pickup coil. that is how autozone has it listed.

also has the crank sensor ever been replaced? i have read that some aftermarket crank sensors have caused check engine lights due to incompatibility with factory ecu.

wjnfirearms

That's the first I heard of aftermarket crank sensors throwing codes. Both XJs we have have new crank sensors and no codes.

Did the guy at AZ clear the codes after he read them? I'd do that and see if they reoccur, especially if it runs a good as you say it does. I'd invest in your own reader. It comes in handy and a basic reader isn't expensive at all. You don't have to invest in a more elaborate device like I did.

jeepxj99

yeah i cant remeber where i read it. but i think it had te be some strange isolated case because i know plenty of ppl with jeeps that had them replaced. i didnt quite believe it myself but they swore it fixed their problem.

GsZ

I also have a 98 Cherokee Sport 4L, and getting the P1391 after running it for a while and then idling for a few minutes. The CEL seems to come on only after engine is hot and I idle for 5 minutes or more.

I used to get a P0340 and eventually the camshaft sensor quit on me (this is also called the ignition pickup coil on the 98). After replacing the camshaft sensor (under the distributor cap), I started getting the P1391. I replaced the Crankshaft sensor with a Mopar sensor, and I still get the P1391, but don't have any timing issues.

According to some other posts, I am looking at replacing the distributor, as it looks like it may come down to that anyway.