Overkill1979

I just bought my first jeep. A 1998 Cherokee with the 4.0 and an automatic 4wd. The check engine light was on so I thought it was something simple. It said it had a cam sensor code. Did some research and saw that it and the crank sensor were both replaced. Just got my Chilton manual and looked at the wiring schematic. I also looked at it on a computer and noticed that the TPS is showing a value at times with the accelerator not being touched. From what I am seeing in the schematic all three go into the ECM. How do I figure if it is the ECM or the harness??? Any info will be greatly appreciated. It runs great, other than the tapping which I was told was a lifter, will inquire about that later.

salad

Welcome to the site!

Before throwing parts at it try the ground refresh listed here: https://www.cherokeeforum.com/f51/cr...x-tips-153657/ Those sensors share some common wiring, sensor grounds need to be ruled out.

That said, TPS failure in that manner is common. Replacement with a Mopar unit is the best course of action. Were the CMPS the CKPS replaced by the previous owner?

VTJeep

well, before going into the PCM, try to verify that the sensors are good. To verify the wiring is good you need to do a continuity test on all the wires involved in the sensor/s you believe to be fouled. This is a timely and tedious and expensive (unless you can do it yourself) process, but will help isolate the issue. If the sensors that were replaced originally were knock off brand or at least cheapo's, then maybe they have fouled due to that. But if sensors are good, and wiring checks out, then may i suggest these guys http://autocomputersystems.com/ I had really good luck with them. Its worth actually calling them because the price may be a bit different than listed and i think its worth rellaying the info to one of their techs directly. good luck man.

Overkill1979

I don't know if it was the previous owners or if they had a shop do it. Found some stuff rigged poorly that I have fixed. How do I go about testing the sensors? How do I find out which one of the three plugs on the ECM those sensors feed into?

salad

There are writeups for testing all of those sensors on here. Go to Google and put stuff like "testing CPS" with "site:cherokeeforum.com" on the end of it and you'll get excellent results.

As for detailed wiring diagrams of all the circuits, that's what the Factory Service Manual is for. Try your favorite search engine, you may find one.

On a 1999 the CMP, CKP, and CPS go into connector C1 on the PCM. Go read through cruiser54's thread on ground refreshing and connector maintenance.

Overkill1979

Ok, will do. Thank you both for all of the info. Once I straighten this out, onto replacing the cracked exhaust manifold.

Overkill1979

Did the grounds like the post suggested, check engine light came on, saw another post that said trace a brown and white wire, havent done that yet. Also saw another post that said they had the same code and that the distributor itself was bad.

Overkill1979

No more check engine light. Put in a new distributor and that fixed my problem. Mine had a little play in it.