XJOdin

I have recently picked up a 2wd 1999 jeep Cherokee XJ with the 4.0L and the aw4 automatic. it runs fine for having 309k miles on it, only an exhaust leak that i have noticed wrong with the motor, and it does not overheat even sitting and idling for more than an hour. now the issue that i am having is that the rig wont move forward under it's own power. it will go into reverse, and move backwards, brakes seem to be fine, transmission shift out into reverse fine, but when i try to drop it into any of the forward gears, it will just kill itself. i'm no stranger to shadetree mechanic work, and the guy i got it from was a little more shady than me, luckily it was only about $100 of my money in it, the rest was trades that came out of my yard, so i am not upset about that. i don't daily any automatics and haven't for years, but when i was in my teens i had a couple, and they never failed me bad enough to drop a gear of quit out completely. now, my first thought was that its an older rig, and i figured i may be able to give her some revs, and drop it from neutral into drive to get it rolling, to no avail. any spare gas it has when it backfires just helps it to get a couple more shots off backwards, blowing smoke out of the breather hose and causing my wife a good scare. I'm not too familiar with the way automatics work to diagnose much farther than the codes that were read on it before i got it. i started with the code i thought would be easiest, which was for the NSS. I removed it and the copper contacts were nice and dull, i shined them up real good with contact cleaner and scotch brite pads, re greased the moving parts with dielectric grease, being careful not to get it on the contacts, and threw it back on. i don't have a multimeter at my house so i couldn't test the wiring, but she looked squeaky clean when i put it back in. pulled the throttle body to clean the carbon out, cleaned off the IAC, MAP, and the TPS, cleaned the contacts at the connectors, dielectric grease around the outside to keep moisture out, and slapped it back on. no change there either. i haven't adjusted the TV cable, though i know that it is all the way in the housing and needs to be adjusted. i assume that the Check Engine light is blown in the dash, as it is not on, and hasn't been since i got it. Things of note: There was 0 ATF in it, thats the first thing i did was fill it up, i also got new plugs for it. the cap, rotor, and wires are all new as well. the oil appears fine using the smell, taste, and look scale us shadetree folks are so accustomed to. she gets good oil pressure, and seems to charge the battery fine as well as stay cool. we rebuilt the fuel pump housing because the fuel gauge on the dash didn't work, and it still doesn't.

TL;DR - 1999 Cherokee 4.0L AW4 309k miles dies when put in any forward gear, but will move in reverse

I'm just kind of at a loss at this point, looking for more ideas to try to get her rolling under her own power again, thanks in advance

codes: P0122 TPS?, P1694 TCM?, and P0705 NSS?

cruiser54

try this.CRUISER'S MOSTLY RENIX TIPS

TRANSMISSION CONNECTOR REFRESHING

OCTOBER 30, 2015 SALAD 22 COMMENTS



Over near the transmission dipstick tube are 2 rather large connectors. One is black and goes to the NSS and the gray connector goes to the transmission itself
. These 2 connectors carry all the info between TPS, TCU, NSS, speed sensor, and transmission solenoids.

Unplug each one, visually inspect for corrosion or bent pins, spray them out with electrical contact cleaner and plug them back in.

Additionally, if your Jeep is an ’87 to ’90 Renix, it’s always a good idea to reach up under the glovebox area and unplug the connector to the TCU and spray it out along with the receptacle of the TCU. While you’re there, find the fuse right in that area for the TCU. Remove it and spray out it’s receptacle and clean any corrosion from the fuse.

Seabee

I am no AW-4 expert, but it sounds like your lock up torque converter is locking when you put it in forward gear. Maybe troubleshoot that condition.

Jim Malcolm

After refreshing the connectors as suggest above, if it still doesn't work properly, disconnnect the TCM, or the grey connnector, or remove the fuse. You'll need to start off in 1st and then shift to 2nd at the appropriate time, but this will eliminate all of the electronics and isolate it to just the mechanical aspects of the transmission. Limp home mode if anything were to ever happen with the electronics...

Roler

Yep good first ideas there to try.
I take it it now has the correct ATF and level?

XJOdin

i made sure to check the ATF in neutral, it is exactly between the full and fill lines. i will refresh the contacts for the transmission harness when i get off work on monday, i have already cleaned the NSS harness and sealed it with dielectric grease, being careful to only get it on the seal and not on the contacts. i will also pull the multi stage ground by the dipstick and clean that up. i will test the mechanical function of the transmission with the fuse and tcm disconnected and see if that makes a difference. with 309k miles on it i wouldn't doubt if it needed a transmission rebuild, i just though it was strange that the rig will move backwards but not forwards. does anyone have info on how to diagnose if the torque converter is locking when i put it into drive? a harness i could back probe, or something similar? thanks for all the help so far!

Jim Malcolm

You can disconnect the grey connector and test the voltage on the respective pins to determine what the TCM is outputting. The TC Lockup is solenoid 3; pin E in the gray connector for the 94 model year...


AW4 Solenoid Connector Pinout