jimmy_wheels

Hi all,

New user here and I'm hoping to get some much needed help. I will be as descriptive as I can.

Ride: 1999 XJ Cherokee 4WD (173k miles)

My issue started with the Check Gauges light. It comes on and off, but mostly it is on. The oil pressure gauge goes to a zero when the light is on and returns to normal when the light is off. It can cycle back and forth multiple times in a matter of minutes.

I also randomly get an Air Bag warning light that comes on and off. That come on less frequently as the Check Gauges light.

I have never noticed any particular driving conditions that are precursors to the lights coming on. It seems very random.

The other problem, and this is a bigger problem because it's costing me money, is the Check Engine Light with a P0705 code. The first time it came on in Dec 2016 I had the transmission rebuilt by a reputable shop. That fixed the problem for about 8 months. Then the same code popped up. This time the same shop said it needed a Neutral Safety Switch NSS. Even though I didn't notice any symptoms of a bad NSS, I purchased a new one from 1A Auto ($46) that they installed. The part had good reviews so I felt solid about it. Well, after only two days and roughly 125 miles of driving, I got another P0705 transmission code. I have no idea if it's the new part, how it was installed, or if it's something else causing the code to keep coming up.

To add additional confusion to my puzzle, I've noticed that my XJ fluctuates RPMs when idling. I was recently backing out of my driveway and I was applying the brakes. All of the sudden the throttle jumped and pushed the vehicle while I was braking, not a good feeling. It will also fluctuate at low speeds. Sounds like a faulty Throttle Position Sensor. Could this create any of my CEL problems or P0705 codes?

So that's where I'm at. Anyone have advice or similar conditions?

I need to update my registration, but can't with a CEL on.

Thanks!

fb97xj1

Doublecheck the NSS using a mutlimeter.

- Set the parking brake and/or use wheel chocks.
- Engine OFF and transmission in Park.
- Disconnect the NSS connector in the engine bay.
- Set the multimeter to ohms (resistance).



Park - continuity should exist between cavity B and C.
Neutral - continuity should exist between cavity B and C.
Drive - there should be no continuity.
Reverse - continuity should exist between cavity A and E.
3rd - continuity should exist between cavity A and G.
1/2 - continuity should exist between cavity A and H.

Doublecheck the NSS (also known as a Transmission Range Sensor) ground as well. There are two grounds near the PCM on the driver side inner fender. A lot of stuff grounds here. Remove and clean/sand to bare metal.



Also, sometimes the NSS does not need replaced. Sometimes they just need disassembled, cleaned and adjusted. The grease in them dries out and cakes with age, causing the NSS to stick and/or lose contact internally, resulting in a trouble code. If you suspect the TPS (which directly effects shifting), you can test the TPS circuit using a multimeter and some safety pins to backprobe the connector. Small pins. Idle troubles or jumping rpm can also be an issue with the IAC, or vacuum leak.



As for the Check Gauges and Airbag light, it could be a bad ground or connection for the gauge cluster. I dont know. Im still learning how the CCD Bus operates and why it does some of the things it does. The electrical system in the XJ is a trainwreck.

jimmy_wheels

Thank you for the very detailed response fb97XJ1. I feel like I have multiple issues going on and it's pretty overwhelming to try and diagnose/fix them all. The main concern I have is the Check Engine light. The only symptom I've noticed when the CEL came on the last two times is that the cruise control doesn't work. Any idea what would be creating that issue?

I agree with your comment about the XJ being a train wreck of electrical system. It's a painful experience for sure.

Waynerd

The airbag light and no cruise is probably a bad clockspring. What about the horn, does it work? Test the TPS and NSS.

Not sure but I think the TPS and oil pressure sensor share a ground. But they could both just be bad.

jimmy_wheels

Bad Clockspring huh? Okay. What's weird though is the cruise control was working when there was no CEL. I wonder if the CEL automatically enacts a shutdown of cruise control?

Yes, the horn does work.

Waynerd

Oh. There's also some issue with the power to the horn or the cruise shorting to the ground for the sensors. It'll mess with the TPS and illuminate the CEL for a false TPS code.

The issue I had was unheard of and I still never figured it out. My TPS was acting up and finally lit the CEL. I changed it and kept getting codes. I also noticed if I turned full right it would stall. I ended up pulling the 2 fuses for the horns and the one for the airbag. I don't have cruise.

I still have fuses removed. No more TPS issues. Train wreck is right. Try pulling any fuses that send power to the steering wheel. Horn, cruise, airbag. See if that helps. It's free and easy. May not solve anything but worth a try.