Need expert AW4 help.

[Z06guy]

Vehicle: 96 4.0 AW4 188,000 miles

Symptoms: With shift lever in OD, sometimes shifts normally, sometimes does not want to upshift. It sometimes stays in second gear up to 75mph. Most of the time it will upshift, but very late. It will also downshift out of over drive on the freeway for no particular reason. Sometimes it will upshift, downshift, upshift, downshift, and sometimes it will just downshift to third and stay there. Converter does lock up.

Testing: With TCM unplugged, it behaves properly, staying in whatever gear I leave the shift lever.

Fluid level is full and fluid color looks very good and smells fine.

Volt meter check of the plug showed everything reading properly with a few exceptions. First, I did not test the VSS input. I've read here that if it's bad, it won't upshift at all.

Second, C14-C16 all show ZERO ohms of resistance at the TCM plug and at the plug at the firewall. This is the part I don't understand. How can the trans shift even simi properly if all three solenoids were dead shorted to ground?

I tracked the little harness all the way to where it goes behind the transfer case shift linkage and don't see any destroyed or melted wires. I did notice at one point in the harness that the wires were a tad wet with tranny fluid inside the black plastic sheath which is odd because I don't have a tranny fuid leak.

Problems started on the trip home after a brutal 12 hour day of hardcore trail running in 105 degree heat. Vehicle was subject to heat, banging around, and a couple splashes through muddy puddles.

Any help you can offer me would be greatly appreciated.

[Z06guy]

Bump.

[98 jeepjeep]

sounds like your solenoids are going out...there are 3 located in the pan..you should have around 11-15 ohms resistance (Key off,tcu unplugged) on pin C14,15,16 with the Neg lead into pin D7...........should you have to replace them...if you can afford it i reccomend doing all 3.
http://www.bulkpart.com/Merchant2/me...e=A340solenoid

On a side note i recently replaced my TCM because it was bad and caused the same exact issues that you were having. But with all my problems trans related i had codes....A faulty TPS could cause issues also...And the NSS is to Make sure the vehicle starts in N or P only...and to work the Reverse lights...

[Z06guy]

Thanks for the reply. I think my problem is my solenoids as well. I just have a hard time believing they are all soo bad they are have absolutely no resistance to ground at all. I would hate to pay the money and go through the effort of changing them only to find my ohm meter or testing procedure was the problem, and the soleniods are fine. I am checking them just as you instruct, though. After that, I checked all three at the plug by the firewall with the other lead on the negative side of the battery and got the same result. I'm going to borrow a different ohm meter and recheck them.

[98 jeepjeep]

Don't forget you need to ground on d7 in the tcm plug. To be sure you have a proper ground.

[kingmeirl]

If you take the solenoids out: Test them by grounding the metal bracket and running 12V to where the connector is. If the solenoid CLICKS once when you apply the 12V then the solenoid is good. If it makes no noise, then it is fried.

[winterbeater]

Understanding ohmeter readings is not that easy. Sometimes a little continuity seems like a lot. You can try to get a feel for this by looking at your readings while touching the probes together, holding them out in the air with no contact, and by holding them in opposite hands with your fingers. This should yield high continuity, no continuity, and very low continuity, in that order. If you only have very low continuity, it would not really be a short.

[bigalpha]

This happened to me. All 3 solenoids were bad. I replaced them with used ones for like $40 and it is fine now.

Go to a junkyard and pull them from another AW4.

[bigalpha]

Originally Posted by kingmeirl

If you take the solenoids out: Test them by grounding the metal bracket and running 12V to where the connector is. If the solenoid CLICKS once when you apply the 12V then the solenoid is good. If it makes no noise, then it is fried.

Also, they should test within the proper ohm range as well.

[Z06guy]

Originally Posted by 98 jeepjeep

Don't forget you need to ground on d7 in the tcm plug. To be sure you have a proper ground.

Yup, that's just what I did when I tested them through the plug.

Originally Posted by winterbeater

Understanding ohmeter readings is not that easy. Sometimes a little continuity seems like a lot. You can try to get a feel for this by looking at your readings while touching the probes together, holding them out in the air with no contact, and by holding them in opposite hands with your fingers. This should yield high continuity, no continuity, and very low continuity, in that order. If you only have very low continuity, it would not really be a short.

That's exactly what I did! I was also looking around the shop for a resistor. Somthing with a known resistance, but couldn't find anything. When holding the probes in opposite fingers, it was reading extremely high resistance. Somthing in the milli ohm range.

[Z06guy]

Okay, I just went out and tested them again the exact same way as before at the plug with the same multimeter and got different reading. Now all three measure exactly .216 k ohms which is 216 ohms. I still don't understand how their reading changed or why they all read exactly the same. Help?

[bigalpha]

Replace them. Mine did this EXACT thing.

[Z06guy]

Okay, I got new info. My tests at the firewall connetor were bogus because I touched the other lead to the positive side of the battery.

Once I used the negative side, all three solenoid leads show 11.2 ohms.


So the question became why does it show 238 ohms using the d7 pin in the connector? Well I checked the resistance between the D7 pin (black wire/ ground) and the negative terminal of the battery and it was 218ohms. In other words, all of my resistance is through the black ground wire in the D7 pin. The resistance through my solenoids is fine to the battery. Now I need to know where that black wire goes. I traced it down the harness to a seperate two wire connetor which runs to the back of the transmission behind the tranfercase shift linkage. Does anybody have the wiring diagram? Can I just jumper that black wire to a solidly grounded bolt?

[Z06guy]

I found a couple wiring diagrams on Pirate4x4 and they both show the D7 black wire just going directly to ground. That's great. It looks like I could simply connect that wire to a known good ground and my problem might be solved. I just have to wonder, why would the manufacture run the ground wire through the harness all the way to the inside of the trans if it was just a ground?

[98 jeepjeep]

find that ground wire it may be corroded/loose the resistance is high..the wire may even be partially cut.