HELP! allready bald and no more hair to pull out

hello all, let me introduce myself. name is Dan from Central PA and i am a new owner of a 97 XJ 4.0 w/ auto. Which will be for sale when i can get this issue resolved and inspected.
reason being, my brother & sister inlaw cannot take care of vehicles or budget their money. so after investing our monies in a motor replacement, tires, new radiator, cat, muffler, exhaust, o2 sensors, windshield, both front window regulator, ect....ect....ect.... (you get the point) they decided to sign over the jeep to us after they popped the second motor. now after a year of delay, i finally did another motorswap with tranny this time. ya see, i have been chasing OBD codes since the original motor was in. the codes are p700, P705, & P1899. used my reader and was leaning toward the NSS so i got a used one and pulled it apart prior to installation. it is almost new inside. hardly any swipe marks or divots like the old one had. so i cleaned it, regreased it with some dielectric grease, adjusted it according to the manual and seems like it was going to work fine. reverse lights work perfect. jeep starts and drives fine, pulls great, shifts thru gears fine. however after it is shut off and restarted, the codes appear. i can clear them, and they will reappear after a short drive and a restart. one thing i can't figure out is that it will start in any gear, which makes me think NSS. but it just can't be. it threw the same codes with the old trans, old trans computer, and the old NSS. all of which were replaced. so i am now thinking harness but i can't find any visible issues anywhere (worn, burnt, or torn areas)
my battery was dead in my voltmeter so i didn't get into testing the voltages yet in the harness.

the definitions off my fancy reader is as follows,

P0700- Auxiliary 5 Volt Output Too Low
P0705- Transmission Range Sensor A Circuit (Park / Reverse / Neutral / Drive / Low Input)
P1899- Park - Neutral Switch

i am really not thinking it is actually the NSS. any chance it could be internal relays or solenoids? or voltage being robbed somewear else? i did find one other person online that had the same issue and his was the result of a remote starter installed on in the harness somewhere. the dealer replaced the NSS for $600 and didn't fix it.

if anyone can give me some sort of other avenues to try i am all over it. and i can't even begin to express my gratitude for any help that is given.

mucho thanks

cheers, dan

I'd look into a short (intentional or accidental) in the NSS harness-- you've changed the hard parts without change in the codes. You're showing that the ECU doesn't have much of an idea what gear it's in and after changing/cleaning the items that tell it what gear you're in, you're looking at a disconnect between the "correct" signal and what the ECU is seeing.

If it wll start in any gear that is the reason for the codes. Will it start with the NSS unplugged at the dipstick connector? That will be a good test of the harnesses.If it will crank with the connector unplugged I would look for a remote starter. Remote starter problem is also a good lead because they are often installed by less than intelligent people. You will have to stop the cranking anytime before the codes will disappear. If you stop the cranking anytime and still have those codes TCUs are cheap at the pick and pull like 10 bucks so it be a good thing to try.

If it starts in any gear, it clearly sounds like there is a short circuit. Someone may have wedged a paper clip inside the NSS harness under the hood back by the firewall passenger side, between pins B and C. Thats all it takes to make it start in any gear, and it will give you the P0705 code.

Had the same on my kids 2000xj. Swaped out the Trans control module. No more code. Found one for $15. I think yours is the same, drivers side foot well above the gas pedal. maybe check the plug?

thanks folks. i had allready replaced the TCU after i put the previous motor in. it was inexpensive and seemed to work for a couple of days then the codes came back. maybe i got a bum one of those. i actually assumed it may have been an internal solenoid or something, so when i was looking for another motor, i was hoping to get a trans combo to eliminate tearing into the guts of it. i did luck out and found one so i must say i was miffed when the codes reappeared when all was said and done. that is why i was thinking it may be something that i haven't touched. no remote starts on this beast & the NSS harness is in good condition but you can't be 100% without a meter. which i will do once i get the batteries.
i am going to try picking up another TCU it is fairly easy to do.

unlike alot of threads online, i will postup the end result when i find it. seems like everytime, no matter what vehicle, when i do research online, the people who start threads, seem to get all kinds of help then never post what ended up being the fix. lots of head scratching. so keep your ideas coming.

cheers, dan

Does it crank with the NSS connector unplugged?

I'm with Shorty, you have issues in the harness somewhere and those issues are killing the TCU as well. If the motor has been swapped its possible the harness could have been crushed and shorted since it is right behind the engine.

absolutely not, i have this motor swap thing down to a science. these 4.0 liters have absolutely no clearance issues anywhere. :dunce:

i will give that a whirl prior to getting another tcu. i wasn't able to get to the place before i left work the last couple days. so i'll try lookin into the harness. thanks for the info and ideas.

cheers, dan

Very odd occurence, I did try and start it with the nss unplugged. It barely turned over, like the battery was dead, then I saw smoke pouring out of the engine bay. I turned it off and took a look.....seems the grounding strap that goes from the firewall to the back of the motor got soooo hot it was burning off some residual oil that had gotten on it.....and I barely was attempting to crank it. Maybe 8-10 seconds. I then waited for the smoke to clear and plugged the nss back in and it cranked and ran fine.....any more idears on where to start in the harness I am going to progress looking into the harness..

Nix last comment. I had the larger trans connector unplugged. Still doesn't make sense why it smoked the grounding strap. But then I did try the nss unplugged it did start.....

for the ground strap to get that hot, you're grounding something to the body that uses A LOT of current or your engine to battery ground strap is in bad shape. That strap is usually only responsible for grounding the body systems to the engine block which then is grounded to the battery.

for the engine to crank with the NSS unplugged, you've definitely got a short to ground in that circuit. The NSS controls the path to ground for the starter relay (only grounded in P or N) and with it disconnected, there shouldn't be any ground for the starter relay to use.

Did the ground strap get hot when you reattached the trans. harness and disconnected the NSS ?

Your negative battery cable does not have a good connection to the engine block. You need to fix this FIRST before you continue with troubleshooting the NSS and smoke something else.

STARTING THE NEW YEAR OFF WELL!
i think I got it figured out. Atleast no codes after a test drive that would typically signal one. Forgive my ignorance, as to why I didn't follow an extra wire from the negative terminal to under the power distribution box. Seems a previous owner had it running to the starter relay and for whatever reason they would have needed it, let it start in any gear and with the nss unplugged. I did go over my grounding points and hopefully have that figured also. I'm gonna drive it for a while and see if i can get the inspection & emissions done on it.I sure I will check back with the outcome thanks again for all the help.
Cheers, Dan

grounding the starter relay directly to the battery? That's an easy way to bypass a bad NSS, but won't pass a safety inspection that way.