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AW4 won't shift out of 1st gear

M

Moo Moo Jeep

NAXJA Forum User
Location
Colonia, NJ
AW4 won't shift out of 1st gear in my 2001 XJ. Reverse works too but that's it. I thought fluid and filter change might help but it didn't. Check engine light is on but it was on even before trany stopped shifting. I tried turning ignition on and off 3 and then 5 times to check for codes but it didn't work. I tried turning ignition on with reset trip button depressed but it only checks all gauges and light on the dash but doesn't show any codes either. At some point check engine light was off but maybe because the battery went dead (aftermarket alarm drains it after a week or so of not starting the Jeep) but now it's on again.
I only drive the Jeep around the block once in the while. I don't have inspection sticker so I would rather not drive to Auto Zone to check for codes. Besides driving it with only 1st gear working would be PITA.

What might be the problem? What should I check 1st? Could TPS be a problem?
 
First gear is when only the #1 shift solenoid is on. Since it stays in first though it could be that the VSS is not seeing speed so it's not letting it shift. Check the wiring on the trans making sure all the proper connections are good.
 
If you pull the TCU or fuse, you should be able to manually shift the tranny if all is well mechanically.
 
I didn't check anything yet but I just bought Professional Diagnostic Tool OBD2 OBD-II ELM327: http://www.amazon.com/gp/product/B00EQ57BE8?psc=1&redirect=true&ref_=od_aui_detailpages00
Can't go wrong if it's only $4.56 with free shipping :) Joe, thanks for info.
 
first: unplug the transmission computer and drive it. 1-2 is first gear, 3 is thrid, d is 4th. go through the gears and make sure everything works. Then, if you can get into third and fourth, check your TPS, just get a new one and put it in. If thats not the issue, you can always return it. If you cant get into third and fourth, it might be your solenoids. In none of that is your issue....its probably a wiring issue or somethings up with your tranny computer.
 
Could be the TPS, like Sideways said.

Could also be the OSS being dead, so the TCU thinks the jeep isn't moving and therefore will stay in first till engine RPMs reach redline or close to it.

I would do what Rudolph suggested to eliminate hydraulics/mechanics as a source of your problem, then check the TPS with a multimeter, if that does not find your problem check the OSS wiring for damage.
 
Not to scare you but I had coolant in my atf. I couldn't really tell by the sample on the dipstick. It was obvious but draining some out of the drain plug.
 
mtbxj87 said:
Not to scare you but I had coolant in my atf. I couldn't really tell by the sample on the dipstick. It was obvious but draining some out of the drain plug.
Click to expand...

:huh: Did the cause your jeep to not want to shift out of first gear? Also if you have coolant in the ATF, that means new radiator time.
 
Rght, I replaced the Rad . I had that issue about 10k miles ago. But yes it wouldn't shift out of 1st gear. Im not saying thatshis problem but its a possibility
 
mtbxj87 said:
Not to scare you but I had coolant in my atf. I couldn't really tell by the sample on the dipstick. It was obvious but draining some out of the drain plug.
Click to expand...

I don't think I have that problem. I just replaced ATF and filter. Fluid was very clean. I'd think I'd notice coolant in ATF. I'll check the coolant level anyway just in case. Thank you for input.
 
XJ_Rudolph said:
first: unplug the transmission computer and drive it. 1-2 is first gear, 3 is thrid, d is 4th. go through the gears and make sure everything works. Then, if you can get into third and fourth, check your TPS, just get a new one and put it in. If thats not the issue, you can always return it. If you cant get into third and fourth, it might be your solenoids. In none of that is your issue....its probably a wiring issue or somethings up with your tranny computer.
Click to expand...

Thank you for the info. Where tranny computer is located?
 
After 2 months I finally checked what's going on :) Fuses are fine. I disconnected TCU and transmission shifts. I don't think I drove fast enough to shift to 4th gear but about 40mph so I guess it shifted to 3rd. I could shift it manually but it also shifted by itself when left in D.

Does it mean TCU is broken or it could be something else like TPS?
 
Last edited:
I had a TPS go bad on me. Would shift in all gears but it was very erratic. Finally after extensive research and trail and error, I changed out the local parts house TPS with genuine Mopar TPS. Cured all my trans issues plus some other issues I was having.

Always use genuine Mopar sensors in your jeep. I didn't and it cost me a lot of time and money.

This is what I used to trouble shoot my issues. Was very helpful. Hope it helps you.

http://mikestrawbridge.com/blog/2011/09/aw4-troubleshooting/
 
Last edited:
It could be a lot of different sensors, wiring, or the TCU. To avoid just throwing money at the problem you really need to test each sensor individually.
 
What about location of TCU fuse? I thought it's under the hood in the fuse box. I found some diagrams and checked different fuses then to be safe I checked all the fuses :) But then after I disconnected TCU I read somewhere TCU fuse is on the TCU harness next to the TCU itself. Is it? I didn't see one when I was disconnecting the TCU but I wasn't looking for it then so maybe I missed it.
 
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