P0705 - Different problem than others

Hey guys I just recently bought a 99 xj 4.0l and got it on the road yesterday, after driving for a little while I got at check engine light, so I read the code and its the P0705, which most say that just clean the NSS and it will be good. But also most of the people with the P0705 are also getting the P0700 which is causing the jeep to lock out Overdrive and only use 3 gears. Well im NOT getting P0700 just P0705 so my overdrive is fine. So I cleaned the NSS and cleared the code, but after driving the check engine light came on again. But I had to follow the jeep in my truck tonight and noticed something weird. Running lights on = normal, touching brakes and rear lights light up = normal, using either turn signal is normal. But when using either turn signal and then pushing the brakes it causes both the reverse lights to light up and flash like the turn signal and when this happens the turn signal stops flashing when the reverse lights start doing the flashing. Let off the brake pedal and it works normal. So what do you guys think, it is what is got to be causing the P0705 since its my only code and issues. Also everything lights up and work right when shifting through the gears on the selector. I have also double check all the bulbs to make sure they are the right ones. Thanks guys let me know what you think, need to get this fixed.

Any time I see lights that when activated, light up other lights I think grounds. Clean them up, and make sure they are in good shape. If you have an ohm meter, test for high resistance.

Sounds very similar to what I experience in my '99 after I Herculined the interior.

My blinkers would work fine, but as soon as I had my lights on, and used the blinker, and the reverse lights would flash. Pressing on the brakes would only give me one bright brake light, and the other would be dull. I also found once that when I had my interior lights on, they started flashing too. I also had a check engine light on I believe (this was a couple years ago now), but I never got it checked.

There should be a ground under the passenger front seat, on the bracing that the front seat mounts bolt too. As soon as I put this ground back (in my case cleaned the extra herculiner off) everything worked fine again.

This is the ground.

The P0700 just means the TCU has a trouble code set. It's not always present. The P0705 indicates the TCU believes the NSS is faulty. Neither will prevent going into 4th or the t/c locking up.

The reverse lights coming on could be causing the TCU trouble code. The line from the NSS feeds both the input on the trans computer and the backup lights. If the computer suddenly sees an input claiming the tranny is in reverse while moving along in a higher gear, that could cause the P0705 code.

I agree that this is likely a bad ground somewhere.

x2 on bad ground. i have been fighting these two codes for the better part of way too long. after removing the after market alarm system and the associated crappy grounding for the alarm and cleaning the factory grounds that i could find, cel finally went away, got my reverse lights back and got od back as well.

Begster, thanks alot for showing the pic of that ground, when I did my Herc I forgot to ground that cable back, I cleaned the herc, hooked the cable, reset the code. And will have to see tonight it if does it again, it seems to only really be noticable at night. I also cleaned the ground in the back behind the panel where the spare tire would be. Ill let yall know.. THANKS again guys

SEEMS TO be fixed, it was just that ground cable under the passenger seat. Thanks alot guys