mlepesant

Hello all,

I am new to posting on the forum. I have an XJ 98, 4.0 with 302k miles with original (almost) and stock for everything.
I have the CEL on and problem shifting. Feels like the car is crawling and doesn't want to shift. I have read a lot about the codes I got but I am stuck with actually checking the solenoids and other electrical related stuff. I have done quite some work on my jeep but anything electrical is a total mystery to me. I am trying to check the solenoids without dropping the pan but can't get my hands on a wiring diagram of the TCU. By the way I have disconnected the TCU harness and drove it and shifted manually, it works fine.
At this point, I am looking at wiring diagrams for the AW4 1989 but the wires colors don't match. I would like to know if I am supposed to check C14, C15, C16 on the harness but I am not sure where they are and ... I really don't know how to use a multimeter . Yeah I know it sounds stupid but that's the way it is; I just don't get it. Could you please give me detailed procedure (detailed, literally...where to put the black lead, where to put the red lead, should the key be on the on or off position, should the battery be disconnected...). I would like also to check the TCU itself and the TPS, but here again same issue, I just don't get how to do it.
Just to give you an idea of the mechanical skills.. I have done the following: replaced rear main seal, one broken valve spring, radiators, rear spring leaves and all the regular stuff (tune up, thermostat, oil change, etc. various gaskets).

Thank you very much for any help I can get. Again, please remember, when it comes to electrical stuff I really feel like an idiot.

Marc

mlepesant

I replaced the TPS, cleared the CEL and drove it for a while. Everything seems fine for now. Hopefully it will stay that way.

Thanks for reading.

mlepesant

That would have been too easy. After 120 miles, the codes are back (although no more P0740, "just" P0700 and P0743. Car drives fine goes through all gears...except 5. Not the same behavior than last time when it became sluggish in 1st and 2nd without going after those. Probably just a coincidence but the light came on exactly at the same spot it came on last time. After 20 miles of driving on the freeway, at the exit ramp, during deceleration...

Does anybody have any idea where I should concentrate next? Either the new TPS is bad, or it is something else and I am at a loss now.

Any suggestions are appreciated.

Marc

KD4315

99% of the time that's your Neutral Safety Switch. Have you take it off and cleaned it yet? Are your reverse lights working? If your NSS is good then I would look at the solenoids in your transmission.

mlepesant

KD4315. Thank you. No the NSS has never been looked at. I will try that tonight and get back. Do you know the best way to test the solenoids without dropping the pan? I tried to test thru the TCM harness but I don't have a wiring diagram and am not sure I am checking the correct wires.
Thanks again.

KD4315

Here's a link to a great write up for the NSS. I'm not sure how to test solenoids without dropping the pan. That might be unavoidable. They're about $200 for a set of 3 and at 300K miles it might be worth it to do a complete fluid flush and change all 3.

http://go.jeep-xj.info/HowtoNSSrebuild.htm

mlepesant

Excellent. Thank you very much. Yes, I am thinking about investing in the solenoids...

mlepesant

I quickly looked under there and there is a drop of transmission fluid on the NSS nut.. I have seen this regularly when I do the engine oil change. I didn't pay more attention than that since the fluid level is ok, I have done it a few hundreds mile ago and check the level regularly. But maybe a leak there is causing some trouble? The reverse lights are working fine.

mlepesant

So, the code came back. Didn't get a chance to clean the NSS but will do that soon. But I clear the code and the car shifts just fine. The code comes back after about 100 miles of driving. I clear the code again and the car shifts fine. Could that still be the NSS, or rather the TCU?

larjerr

Unhook the roundish black connector in the engine compartment near the tranny dipstick(7 wires). Coming from the transmission, the pin you wanna check with the ohmmeter (black lead to battery negative, red lead to pin) is the one with white wire with black stripe. Should read 11-15 ohms, if not inspect the wiring . I ordered solenoid 3, part # 5016121AA and believe this will solve my problem. The two pins next on the row, tannish with white stripe and bluish with white stripe, the other two solenoids, should also read 11-15 ohms.

mlepesant

Thanks. I am getting there slowly too... Codes came back today after 300 miles of no problem at all. Couldn't go to OD. I'll test the solenoids this weekend and will order one, maybe the set of 3, as long as I am in there..

Radi

The solenoids have been known to fail once they get good and hot. (but test fine when they are cold).

larjerr

Please don't order all three before you check the resistances! The only one that is suspect is the number 3, the converter clutch solenoid, that the only one throwing the code. I checked mine and got 36 ohms and just went ahead and ordered the part. It could be I unbutton the pan and find bad contact in the connector to solenoid inside transmission, but I'd doubt it. The wires going into the tranny looked Ok and 36 ohms just seems more like a bad solenoid than a wire short.

PS, I'm working with a 98 xj, your wires might be different on a 2001.

mlepesant

I just checked it. 162 ohms on #3...I inspected the wiring as much as I could and couldn't see anything special. I'll go ahead and order just this one and replaced. I am working with a 98 XJ as well so wire color was right on! I'll update once I replace it. Next weekend if I get the part on time. Thanks again for the great help.

larjerr

Kewl man, I was/am having the same problem, got my part today. Might do it tommorrow. Keep us updated, I'll do the same. I'm not gonna say the NSS couldn't have an effect, I know my reverse lights have been flaky for years. Let's hope the TCU isn't lying to us. Only thing I know for sure is the solenoid is malfunctioning. I hope it is that simple.