• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

AW4 issues

1

1369jayson

NAXJA Forum User
Location
Bozeman MT
Hey all I hate to be the "FNG" who comes on with a problem, but I am afraid if I cant get this figured out then I may suffer a fatal aneurysm.

I have an 1996 XJ Country 4.0 AW4 4x4. I bought it about a year ago and I have been having a shifting problem since day 1. When driving at highway speeds after the vechicle has warmed up completely it will shift out of overdrive, if you press the gas petal it will shift back into overdrive but as soon as you let up slightly it will drop back out. If you are driving a good distance 50+ miles it will occasionaly drop all the way to second without changing the position of the throttle. When you pull over and put it into park, shut the engine off and restart it will operate fine for a few miles then start dropping out of overdrive again. Also occasionaly when driving in the city the transmission will not down shift out of 3rd or 4th when stopping at stop lights, if you move the selector to 1/2 then up to 3 it works fine. When I first bought the Jeep I pulled the transmission plug drained the oil, filled with new and drove for about 250 miles then pulled the pan and changed the filter and oil. I drove about 3000 miles and changed the filter and fluid again. Nothing ever looked wrong with the fluid I changed other than the first time when it was burnt. I have been doing research and have already checked and replaced my Throttle Position Sensor. I have adjusted the TV cable that is controlled by the throttle lever. I have also replaced all 3 shift soleniods (resistance was a little out of spec) I have also checked the fuses and connectors. The only other thing that I can think could be causing the issues is the TCM/U, or the tranny is working on dying. Any feed back that could possibly shed some light on my situation is greatly appreciated.

Thanks and Semper Fi
Jayson
 
First let me say that my experience has been with the old Renix systems so this may not apply to yours but I had a similar problem and found that the TPS was bad. On the older models the throttle position sensor has a separate side for the AW4 and while the main computer was getting a proper tps reading, the tranny side was all over the place causing similar shifting problems. New TPS and the problem completely went away.

HTH
Todd
 
Cheap TPS from IdiotZone/Advance/O'Reilly's/eBay have been proven to be out of specification or even faulty right out of the box. They also tend to have a short service life.

You should start with a Genuine JEEP TPS. Check the TPS wire plug and wires for dirty connections, failed wire splices, and melted or damaged wire insulation. Consider cleaning and adjusting the NSS, and finding a used TCU to install as a test.
 
Sounds like most of the things have been covered already, except the brake switch that tells the TCU when to lock and unlock the TC, and down shift, and maybe the VSS that both the PCM and TCU use.

Have you check for codes? Might try a new style USB box ($20 on Ebay), with a laptop, software and live data!!!!!
 
Well I did the obvious check of the brake switch a couple of days ago (driving down the road with my toe pulling up on the brake petal) and it didnt make a difference. What exactly is the VSS and PCM? What is the USB box called so I can search on ebay.
 
VSS = Vehicle speed sensor, the computer uses it determine vehicle speed. Sometimes used to determine engine load, transmission shift points.....

PCM = the engine computer, controls engine timing, use to be called an ECU, Engine control unit (87 to 95?), now called a power control module, since 1996 IIRC.

Forebay just search google with "OBD-II scanner, USB laptop"

https://www.google.com/search?q=OBD-II+scanner%2C+USB+laptop&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:eek:fficial&client=firefox-a#q=OBD-II+scanner%2C+USB+laptop&hl=en&client=firefox-a&hs=6kK&rls=org.mozilla:en-US:eek:fficial&prmd=imvns&source=univ&tbm=shop&tbo=u&sa=X&ei=ue8aT5bDJcHc0QGDrqmmCw&ved=0CKABEK0E&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=a6b0194754651294&biw=1280&bih=587

You need to actually test test the brake switch with an ohm meter, to see if it goes from open-closed-open, when you activate the switch from on-off-on. The test you did proves nothing about the switch.
 
Before you go and buy all sorts of eBay stuff, start with basic diagnostics using an $8-12 volts/ohms multi-meter and check some of the common causes of transmission issues.

Use the Google and find an AW-4 Service and Diagnostics manual.

Test the TPS and inspect the wires. Inspect the wires and wire plugs to the speed sensors on the transmission, and speedometer output on the transfer case.

Re-adjust the transmission control cable. Cherokees have a half round push button cable lock on the transmission control cable. Push the half round button located on the cable/valve cover bracket and push the cable into the sleeve. From the drivers seat, push the gas pedal all the way to the floor.

You may have to adjust the automatic transmission cable a couple of times for correct transmission operation.


If everything looks good and the TPS test correctly, consider a used TCU, they are fairly cheap at the junkyard.

TPS TEST

You should have 5 volts going into the Throttle Position Sensor (TPS). It is best to use an analog meter (not digital) to see if the transition from idle to WOT is smooth with no dead spots. With your meter set for volts, put the black probe on a good ground like your negative battery terminal. With the key on, engine not running, test with the red probe of your meter (install a paper clip into the back of the plug of the TPS) to see which wire has the 5 volts. At idle, TPS output voltage should be greater than .26 volts but less than .95 volts. Move the throttle and look for smooth meter response up to the 4.49 at WOT. The other wire will be the ground and should show no voltage.

Perform the test procedure again and wiggle and/or tap on the TPS while you watch the meter. If you notice any flat spots or abrupt changes in the meter readings, replace the TPS.
 
Last edited:
Jeesh, read post #1 by the OP before sticking foot in mouth, LOL!!!:twak:


I have been doing research and have already checked and replaced my Throttle Position Sensor. I have adjusted the TV cable that is controlled by the throttle lever. I have also replaced all 3 shift soleniods (resistance was a little out of spec) I have also checked the fuses and connectors. The only other thing that I can think could be causing the issues is the TCM/U, or the tranny is working on dying
Click to expand...

Tim_MN said:
Before you go and buy all sorts of eBay stuff, start with basic diagnostics using an $8-12 volts/ohms multi-meter and check some of the common causes of transmission issues.

Use the Google and find an AW-4 Service and Diagnostics manual.

Test the TPS and inspect the wires. Inspect the wires and wire plugs to the speed sensors on the transmission, and speedometer output on the transfer case.

Re-adjust the transmission control cable. Cherokees have a half round push button cable lock on the transmission control cable. Push the half round button located on the cable/valve cover bracket and push the cable into the sleeve. From the drivers seat, push the gas pedal all the way to the floor.

You may have to adjust the automatic transmission cable a couple of times for correct transmission operation.


If everything looks good and the TPS test correctly, consider a used TCU, they are fairly cheap at the junkyard.

TPS TEST

You should have 5 volts going into the Throttle Position Sensor (TPS). It is best to use an analog meter (not digital) to see if the transition from idle to WOT is smooth with no dead spots. With your meter set for volts, put the black probe on a good ground like your negative battery terminal. With the key on, engine not running, test with the red probe of your meter (install a paper clip into the back of the plug of the TPS) to see which wire has the 5 volts. At idle, TPS output voltage should be greater than .26 volts but less than .95 volts. Move the throttle and look for smooth meter response up to the 4.49 at WOT. The other wire will be the ground and should show no voltage.

Perform the test procedure again and wiggle and/or tap on the TPS while you watch the meter. If you notice any flat spots or abrupt changes in the meter readings, replace the TPS.
Click to expand...
 
Last edited:
There was another post / thread this week where the guy seemed to solve his problem finally buy disconnected the 2 large gray bulky wiring connectors near the oil dip stick that run to the NSS and AW4, from the wiring harness (ECU/TCU..). He washed the connections out with electrical cleaner aerosol, and washed off the wires and his bizzare shifting issues stopped until he drug the jeep through mud :eek: again, LOL!!!

Edit: I have a suggestion, #2, get a pint of trans-x, add it to the fluid, run it about 1-2 hours, drive it, or idle it in D with parking brakes on and tire stops. then drain and refill with Dex III only.

What fluid did you use on the first two transfusions? Also, several posters fixed similar problems by fixing a bad Transmission case ground. I don't know the exact details, but they are in recent (last 12 months) threads here on AW$ shifting problems. The bad ground (it would come and go!!!!) affected solenoid operation on the non renix jeeps!!!!!
 
Last edited:
Ecomike said:
There was another post / thread this week where the guy seemed to solve his problem finally buy disconnected the 2 large gray bulky wiring connectors near the oil dip stick that run to the NSS and AW4, from the wiring harness (ECU/TCU..). He washed the connections out with electrical cleaner aerosol, and washed off the wires and his bizzare shifting issues stopped until he drug the jeep through mud :eek: again, LOL!!!

The connectors are actually near the trans dipstick tube. I have also solved some shifting problems doing the connector refreshing there. Those 2 connectors are the information superhighway between the NSS, TPS, TCU etc.
Click to expand...
 
Tim_MN said:
Cheap TPS from IdiotZone/Advance/O'Reilly's/eBay have been proven to be out of specification or even faulty right out of the box. They also tend to have a short service life.

You should start with a Genuine JEEP TPS. Check the TPS wire plug and wires for dirty connections, failed wire splices, and melted or damaged wire insulation. Consider cleaning and adjusting the NSS, and finding a used TCU to install as a test.
Click to expand...

I've had issues with the TPS on my '96 Country also, but I was lucky as it threw a code when it started acting up. I bought a new one, Standard brand from Rock Auto, the more costly of the two Standards offered, and it actually acted worse than the original 'bad' one. I pulled a bunch from the junkyard, and after trial and error, found one the engine is happy with. Vehicle was stumbling, then accelerating on its own, tranny couldn't make up its mind on the highway, but seems happy now.

The problem started after the 're-flash' recall, and I've since asked the dealer that performed it just what it was meant to do. They had no idea what or why, and I've since read here that some folks have had bad luck with it. I think that the '96, being the first year of OBDII, is the guinea pig, as our older XJs have not had the same issues.
 
Just because he bought new a TPS doesn't mean the new one is working correctly or he didn't dislodges a pin in the connector installing it. Adjusting the TV cable doesn't always get it right on the first attempt. One should always start with confirming the basics and then work your way deeper into the diagnostics.
 
Yeah I was the guy who was having similar problems with my aw4 last week...thought I was screwed and had to buy a new one until cruiser54 saved the day.

Try what he said, near the dipstick tube is a couple of connectors, one is gray and black and the other is black, both female and male are black. Disconnect both of those and spray Electronic Cleaner in there and let it dry for a couple mins connect it back up and test it out.

Also, not sure if you've already tried disconnecting your TCU and shifting manually. This is how I found out mine wasn't mechanical....I could shift perfectly fine manually...

Goodluck!!!
 
You must log in or register to reply here.

Similar threads

B
Jeep xj surging
Replies
11
Views
433
Bmfinney
B
Jeep70
96 XJ Transmission issues
Replies
3
Views
57
RCP Phx
R
C
Transmission Not Shifting Past First Gear
Replies
2
Views
70
CBJeeper
C
J
AW4 Problem shifting first to second when hot
Replies
2
Views
1K
cruiser54
C
Z
Whirring sound only heard from inside
Replies
7
Views
114
Z.m4v
Z
Back
Top