Ok, so still working all the bugs out of my ZJ. I have been throwing a CEL code since i purchased this vehicle. My scanner pulls P1391 which autozone will tell you is "engine missfire." So i replaced 75 percent of the ignition system. plugs, wires, rotor button, distributor cap. Cleared the code and went along my day. Threw the same code later that day. Did some more research and P1391 is a code for "intermittent loss of cam or crankshaft position sensor" so...i replaced both of these units. which btw is very difficult to replace the crankshaft position sensor unless you have 5 feet of extensions for you ratchet and a swivel, or the arms of a 12 year old girl. luckily i have a pretty nice selection of ratchet extensions. So sensors replaced, cleared code, 2 hours later threw same code again. at this point i'm $200 into chasing this CEL and have solved nothing. Not a total loss...pretty nice tune up job on the truck...but still staring at the CEL on the dash.

Any ideas out there? The counterdrone at Autozone tells me the timing chain or timing belt may have jumped causing the code, but the engine runs great so i seriously doubt this is the case. Any help would be greatly appreciated!!!!


Dub

 

The light will disappear after 50 key start cycles with no recurrence. If you can't wait, you can remove the bat cables and hold them together for 15-20 seconds. That will drain any residual charge in the ECM and erase the codes. After reconnecting the cables, drive for about 20 miles so that it can relearn the systems parameters. You will get a code 12 if you check them after this. Here's how you can check the codes yourself. >->Jeep Horizons :: View topic - Jeep Computer codes (OBDI & OBDII
Dan

 

does erasing the codes with the scan tool not accomplish the same thing? I will attempt the battery disconnect tonight. I truly hope that i haven't been doing all of this and fixed the problem a long time ago. I don't like not knowing what it was i did to fix a problem. Thanks for your response!

 

No the scan tool won't erase the codes automatically. That's why I read my own codes.

 

Is this a V8?
If the distributor on the V8 is moved three degrees in advance or retard it will cause this code to appear. You stated you got the vehicle and it had this from the start. Perhaps someone may have moved it or even had it out to replace leaking seal. Also braided copper ground wire on left rear of engine is a common break/corroasion problem which will also cause this code.
Another common problem is a short on the 5 volt reference circuit which is every sensor on the engine, but because the cam sensor is a hall effect sensor it quickly drops out of signal.
Let me know....OK

 

not a v8. its the 4.0L. are you familiar with the 4.0? are any of these instances the same with the 4.0L. I can't really imagine the timing is off considering how smooth the engine runs. i have no problems with the engine running at all. OH...I will say this though, the spark plugs looked as if they were burnt when i replaced them. not bad, but they were fairly new plugs and the ceramic surrounding the electrode was brown. don't know if timing would cause this, or just the engine running lean. Going to try disconnecting the battery tomorrow morning and if i throw the code again i'll go pick up a timing gun and check the timing. Thanks for your input.