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renix aw4 losing tcc lock up again...

Hellbent

Hellbent

NAXJA Forum User
Location
san diego, california
ok.....so, a while back i had issues with my aw4's tcc suddenly not wanting to lock up about 75% of the time. after a bunch of troubleshooting, i swapped in a used #3 solenoid that tested good.
after this, it started working properly for a few months. it has recently stopped working "most of the time" again.
other than the lock-up, the transmission shifts/drives perfectly.
i have just discovered something that i think is an....or the issue.
if i check the resistance of the solenoids from the white connector in the engine compartment, i get infinite resistance between the "b" terminal(ground) and ANY of the three solenoid terminals(e, f, or g). if I test between e, f, or g and the battery neg post(or the engine block), i get about 15.8 ohms on all three when the tranny is hot.
check between any of those and the b ground wire.....i get infinite resistance.
it would seem that there is an issue with that ground wire somewhere between the plug and the tranny/solenoids, yes?
something about this just doesn't seem right though, since all other solenoid related functions work properly.
anyone have some input on this....?
 
Sounds like a bad ground contact at the gang of ground wires at the oil dip stick to me.
 
as part of what i'm fixing and testing, i'm going to cut off the ends of all the wires that ground to that stud, put new fresh terminals on them and heat shrink the ends. i've cleaned that bunch in the past, but the wire-to-ring terminal area on all of them are pretty old and ugly/cracked/etc.
 
My 87 is still there at 288,000 miles but I got fed up with the 89 doing no start debugging one day and just rerouted all but the starter ground wire going there, straight to the battery post. It did not help at the time but made them far easier to check....and clean.
 
now here's something else interesting...
i went around checking different grounds to see how much resistance i was getting through different parts of the harness.
everything looks good, except that ground wire going down to the solenoids from the tcu harness white plug reads infinite. ALSO, i have discovered that the ground terminal "d" on the tcu plug of the tps also reads infinite when checking it's resistance back to the neg terminal of the battery.
this is surprising considering how well it drives/shifts aside from the torque converter not locking.
definitely looks like i need to do some digging around with the wiring.
 
Make sure the brake switch is opening/closing when it should. The one above the brake light switch
 
Hellbent said:
now here's something else interesting...
i went around checking different grounds to see how much resistance i was getting through different parts of the harness.
everything looks good, except that ground wire going down to the solenoids from the tcu harness white plug reads infinite. ALSO, i have discovered that the ground terminal "d" on the tcu plug of the tps also reads infinite when checking it's resistance back to the neg terminal of the battery.
this is surprising considering how well it drives/shifts aside from the torque converter not locking.
definitely looks like i need to do some digging around with the wiring.
Click to expand...

Is the TPS ground wire to the Bat Neg post also infinite? You do have the meter on a high enough scale to read that high?

Does sound odd and very interesting. I ran new ground wires straight from the battery neg post to both sides of my Renix TPS on my 87. Did not want to unwrap and locate the poor AMC crimp job grounds I learned about here years later, left that way..

Have you gone through the Cruiser54 Renix tips on wiring repairs, such as cleaning and tightening things like ground gang crimps in the harness? What year is your renix?
 
mtbxj87 said:
Make sure the brake switch is opening/closing when it should. The one above the brake light switch
Click to expand...

Good suggestion, but he does an obvious ground issue as well
 
i have checked the switch on the pedal(actually pulled it, cleaned, and reassembled the last time i had issues). it is currently still making/breaking contact when it should. :thumbup:
and yes, the tps ground registers as basically open between the plug and the battery terminal.
i'm using the meter on it's lowest setting of 200, but using any of the resistance settings results in an infinite reading. i have done some of the tips, need to get around to doing them all though.
jeep is an '88, still has the c101, but i have cleaned it VERY thoroughly and applied contact enhancer to the terminals.
at some point later today, i'm going to dig into the wiring....among other things, i'm going to check and fix those duct tape covered crimps in the harness. also going to run separate independent grounds for both sides of the tps.
of note: i drove the jeep earlier today, went down a 2 mile long, patchy, uneven, pothole-laden terrible road at fairly high speed. immediately following this, the converter started locking up properly for the rest of the day. i noticed that the transmission was shifting slightly(but noticeably) firmer, and earlier than usual.
 
Last edited:
i have refreshed both the trans connectors by the firewall-no change in anything.
after the severely bumpy road the other day, the tcc worked properly for the rest of the day. i checked the resistance on the B terminal of the light colored plug near the firewall as soon as i got home. between that ground terminal(the trans side of the plug) and the neg battery terminal, i got a reading of 28 ohms. obviously that's far too high a reading, but the tcc lockup was working. the next morning, no lockup again and an infinite reading when i checked that plug again.
it would appear that my problem is somewhere between that plug and wherever that black wire goes into/on the tranny.
i tried wiggling, yanking, twisting that harness-made no difference. i carefully inspected that harness as well as i could access most of it....found no breaks.
does anyone know where that black wire goes, what it connects to? i can't see anything where it disappears behind the bracketry bolted to the side of the tranny.
 
ok, checked there.....good too.
seems i've been chasing my tail with the black wire on the tranny side of the white plug; going over the aw4 fsm, that wire is simply the speed sensor ground back up to the harness-there should not be continuity to ground TOWARD the trans.
i soldered the dipstick tube ground ring terminals, the duct tape wrapped splices by the firewall, added an independent ground directly off both tps ground wires by the plug(adding one to the ecu plug caused a 2500 rpm idle no matter what. so i removed it. no idea what that was all about).
after all that, my idle is slightly lower than it was(was a tad high to begin with), engine is more peppy, and i have great grounds pretty much everywhere now.
still no lock up though. solenoids all ohm out good-hot or cold.
i need to verify that i am still getting a lock up signal from the tcu(I was back when I had the original issue with the #3 solenoid a few months ago), and go from there.
it's a bit frustrating... 😕
 
the pins all look good, tight....clean.
just to double check-the tcu case itself does not need to be grounded/bolted down? i have the lower part of the dash off, and the tcu simply sitting on the floormat for now.
i've checked the grounds, power in, and solenoid resistance from the tcu connector under the dash-everything checks out a-ok.
going to go for a drive in a bit with a voltmeter backprobed into the tcc signal wire to make sure i'm getting the signal when i'm supposed to.
doesn't really matter, but the tcu is not the original one. the original one was accidentally left out in the rain when i first got the jeep. current tcu is out of an '89 or '90.....i don't recall. supposedly they're all the same 87-90...
 
cruiser54 said:
87 to 90 are interchangeable. I like what you're doing with the voltmeter. Is the signal being sent from the TCU?

I have plenty of TCUs if you need one.
Click to expand...

At first I thought his problem was a ground to solenoid 3, but now that I think about it all the solenoids should share a common ground, so the problem should be too little voltage getting to the solenoid (which could be the TCU or even bad data from the VSS? or ECU? or just a bad wire or connector issue) or a bad solenoid or a bad torque converter.
 
Ecomike said:
At first I thought his problem was a ground to solenoid 3, but now that I think about it all the solenoids should share a common ground, so the problem should be too little voltage getting to the solenoid (which could be the TCU or even bad data from the VSS? or ECU? or just a bad wire or connector issue) or a bad solenoid or a bad torque converter.
Click to expand...

exactly where my thinking was.....and now is.
haven't had a chance to go for a drive and see if i'm getting voltage out of the tcu to the #3 solenoid, and if so-WHAT voltage.
just for fun, here's what the inside of a tcu looks like. the four larger transistors ARE connected to the case, but i *think* that's just for heatsink purposes....?
20160614_161804_HDR_zpsscpmmscd.jpg

20160614_161838_zpsejaju7kh.jpg
 
Nice!!!
 
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