AW4 solenoids...which is which

FIgured out my transmission problem is a bad #3 solenoid.

It's an '87 MJ AW4 and the scanner shows #3 bad.

But which one is #3?

I did some searching (admittedly not a lot) but it seems most of the writeups I saw pertained to the later models and listed the solenoids as A B or C etc.

Just get all 3 solenoids from a junkyard unit and replace all 3 of them.

what if one of those junkyard units is bad though...

You can test the resistance of the junkyard units before you put 'em in. Also, I think you can apply 12V to see if the solenoid will engage.

Not to mention, the probability of them being bad is small. It's not a common failure item.

I still had my 2wd trans from when I completed the 4wd swap a few weeks ago. Since I didn't get info right away and had to fix it I did just swap all 3 out from my 2wd trans. So far so good.

Thanks for the responses though...I thought maybe I smelled bad and no one wanted to help! LOL

bigalpha said:

You can test the resistance of the junkyard units before you put 'em in. Also, I think you can apply 12V to see if the solenoid will engage.

Not to mention, the probability of them being bad is small. It's not a common failure item.

Click to expand...

You can test them with a 9 V battery. And although AW4 failures are rare, when they do fail, the solenoids are frequently the cause.

Ecomike said:

You can test them with a 9 V battery. And although AW4 failures are rare, when they do fail, the solenoids are frequently the cause.

Click to expand...

I didnt know a 9V would be enough to test it, cool. And yes, I think that most of the AW4 failure threads I have seen were about the solenoids, too. I know I had to replace all 3 in my last XJ.

Well now it's all acting up again.

We determined the #3 solenoid is for convertor lockup.

MJ has been fine for over a week now...after replacing all 3 solenoids. THen today it began to shift into and out of gears erratically again. It does it the worst when in OD but also does it when in 3rd.

Hooked it up to the scanner and it showed the #3 solenoid being bad again. I know it was good as I pulled it from a good trans. We plan to do the 9V test on the 3 solenoids I pulled from this but I know the 3 I put back in were good as they came from a good working trans.

I even put in a spare TCU and nothing changed. I have cleaned all the connectors in the engine bay and greased them and put them back together. I have not checked the solenoid wires where they enter the tranny pan but I am thinking there is no actual connector there...the wires just run through a grommet/seal there right?

So being as the #3 solenoid is for lockup...the scanner obviously shows lockup as OFF while driving...and of course the #3 solenoid is OFF while driving too.

I am hoping to not have to take it to a shop...so if anyone has an advice etc it is much appreciated.

Have you checked the resistance in the lines between each connector and the trans? That may help you narrow down the problem to a specific section of wiring.

That is our next step. I am truly hoping it is an electrical issue and not something else inside the trans like something caught somewhere inside causing lack of pressure. If that were the case I would think the solenoid would at least still try to come on and then just shut off when it 'couldn't' do its job...but it's not even doing that.

Does anyone think the non lockup issue would cause it to jump back and forth between gears? I know the renix system is tricky and pretty much anything is possible...?

Now for some more information.

Left the battery disco'd last night. Put it back on this morning and then unplugged the TCU to force manual shifting...I wanted to see if it would shift manually...and it did minus 2nd gear and of course minus TC lock.

Plugged the TCU back in and then a short while later the 'current fault' for solenoid 3 went away (the stored fault was still there) and solenoid 3 began to work and lockup was achieved.

I drove it for 20 minutes or so doing full throttle take offs, slow speed, high speed and everything in between. TC locked every time and it did not jump gears.

I took it to the store and shut it off...was inside 5 minutes. Came back out...now the 'current fault' for solenoid 3 was back (it wasn't acting goofy yet) and the TC would not lock and it showed 'lock off' and 'solenoid 3 off' again. Drove it a mile+ down the road and the fault went away and solenoid 3 began to work and lockup achieved. Drove it around a little more and it worked fine.

THen I had an epiphany...I took for granted with my old 2wd trans that the convertor was locking up...I do NOT believe it was...as that trans never gave me any problems for the 6 months I drove on it. Based on the RPMs at xxMPH now vs with the 2wd trans and up until now with the 4wd trans...it wasn't locking. NOW I can feel it and watch the RPM drop when it happens.

It seems to be an electrical issue somewhere...God willing it's not something inside the trans. We tested the resistance on the solenoids I removed from this trans and they all measured correctly...and I am guessing the ones I put back in are also good.

FWIW - you'll only get 2nd gear after you put it in 1-2 and rev it up to like 4000RPM.

When you get the fault error for solenoid 3, test the resistance from the TCU plug to ground. If it's out of whack, test it from each plug that you can find to ground. You should test through ground on the harness. Also, test the ground from the harness to the battery.

TPS or the brake switch signal to the TCU maybe going bad, but since you have a scanner????, not sure what the scanner data means? What scanner?

The scanner shows the TPS as fine (.68v) and the brake switch shows as pressed/released as it should (on the scanner).

We do plan to test everything we can test...first I plan to test the #3 solenoid wire as close to the solenoid (just outside the trans) as possible while driving to see what happens when it shows a 'current fault'. If voltage is making it that far then the solenoid itself may be bad (which I am doubting) or something else inside the trans (debris stuck or moving around inside). If voltage is not making it that far then I will test up the line until I figure out where the voltage stops.

If I am correct in that the 2wd trans was also not achieving lockup then it must be something outside the trans causing the issue.

Oh and it's a snap-on mt2500.

Don't put too much faith in the scanner results. They can be miss leading sometimes. There are two sets of wires on the break switch, the scanner may be reading the wrong set of wires, the tail light wires to indicate the brake switch is working. I prefer to go wire by wire, and check ohms with power off, and volts with power on. I finally installed a toggle switch and LED light on my TCU and Solenoid #3 to verify when the TC was locked and unlocked.

Question is what is a current fault for Sol#3, and what does it really tell us exactly. Where is the scanner getting that data, directly from the wires, if so where in the wiring, or is it from the TCU, in which case what exactly is the TCU seeing or not seeing???

Could just be a faulty transmission ground?

"current fault" just means there is a fault right now. Obviously it doesn't tell us what the fault is. I realize the scanner doesn't tell me everything or exactly what is wrong but it sure gives me a good idea of where to look.

I do intend to check everything needed BUT at the moment it is working as it should. I can feel lockup, see the RPM drop as it should be (in D and OD) and the scanner shows the #3 solenoid to be working and lockup to be working. Also...the 'stored fault' for the #3 solenoid is now gone as is the 'current fault'.

I have a wire spliced into the #3 solenoid wire running into the cab to a multimeter...the wire is less than 15" from where the wiring enters the tranny to go to the solenoids. So when it starts to act up again (if it does) I can see if the solenoid is getting voltage or not...if it is...then I am guessing something inside the trans is unfortunately wrong. If it doesn't get voltage then I am guessing it truly is something electrical outside the trans.

So now I play the waiting game...I drive it hooked up until it acts up again. I am really hoping that all the messing with stuff has 'fixed' it...this is the first time since putting this trans in 2 months ago that it is acting right.

So you are saying "Current" does not refer to an electrical current, and current fault does not mean excess or too little current, as in a short or open circuit?

Ecomike said:

So you are saying "Current" does not refer to an electrical current, and current fault does not mean excess or too little current, as in a short or open circuit?

Click to expand...

Right...it just means that currently (as in right now) there is a fault. This scanner shows current and/or stored faults. It doesn't go so far as to tell you what is actually wrong.

I drove it today...only about 10 miles round trip with no issues...still showing no faults and it had lockup and no crazy shifting. So YAY!

Tomorrow I have to go to work which is 35 miles round trip...so we'll see if it acts up. That is where the multimeter hooked up comes in...that will tell me if I am getting current or not (and how much) if/when the fault occurs on the solenoid.

Still a-ok?

y entonces? cual era la falla?