Torque Converter Unlocking - Wheel Speed Sensors & ABS

Layson · May 20, 2013

Guys,
Need some input on an issue I have been having. Torque converter is unlocking and relocking at speeds above 45 mph or so. It is a BTS trans, No lights on the dash, nothing, still shifts fine.

So I hooked up AE and I only got one real code which I think is unrelated.
P1876 - Transfer Case 2-Wheel Drive Solenoid Circuit Failure

Then I opened up the ABS module in AE and watched the wheel speed sensors. The rear VSS is reading correct but the front two ABS sensors in the wheel bearings are consistently low. They are pretty close as you start out but once you get going they end up being about 7 mph low compared to the rear VSS. Then I see them spike to like 85 mph when I am going 55-60 mph. Only one side will spike.

What I have done so far is swapped out the TPS and that really didn't change anything. Unhooked the alternator and drove to make sure it wasn't creating some kind of issue. Then I reconnected the batteries and made sure it all is nice and tight! I also pulled off the front wheels and brakes and inspected the ABS sensors in the wheel bearings. They looked good.

I am thinking it must be the ABS module going bad? Maybe it is on its way out? I don't know why the front ABS sensors are both off and pretty much the same. I have pulled these up before in AE and all three where the same readings. Anyone experience something similar or want to explain to me how the PCM and ABS takes in all this data? I am thinking that since the front ABS readings are so far off it is messing with the torque converter lock and unlock..... Any help would be great. :thumbsup:

JLDickmon · May 20, 2013

nah..
front wheel bearings

Layson · May 20, 2013

The bearings feel nice and tight. Pulled out the sensors and no metal on them either. It is a strange deal. They are both the same MPH difference off the rear. The rear matches right up with a GPS.

Pstroke96 · May 20, 2013

i dont know if its related but... i had led tail light bulbs in my truck and one of the bases melted, so when i put the headlights or turnsignal on it was shorting to the brake light circut which unlocks the converter, just a thought

Layson · May 20, 2013

I looked at that, I checked the brake lights and they all worked fine. No LED's except for the 3rd brake light on the cab. I might just check that again...

Layson · May 20, 2013

I wonder if I can just disconnect the front ABS sensors and see if that fixes the issue. At least then I know that it is related to my torque converter unlocking...

Mark Kovalsky · May 20, 2013

Layson said:
No LED's except for the 3rd brake light on the cab.

That could be the problem right there.

Layson · May 20, 2013

Hmmm I think I still have the old one. I will throw it in and try it out. Thanks Mark!

bigbeanOBS · May 20, 2013

Check tail lights if a light is burned out happen to me or brake lights Al's the plug on side of transfer as causes strang things un plug and clean it mine is um plugged bug use it was lockin my converter

TyCorr · May 20, 2013

Thats interesting that causes an issue like that. Makes sense but isnt the first thought I had.

Layson · May 21, 2013

Well I installed my old third brake light back in and I will pick up a new bulb tonight for it.

Anybody have any idea on how the ABS module and the computer work together. I remember from somewhere that those three sensors need to be real close to the same number and if not it throws things off?? It is just odd that the two front ABS sensors read about the same and they are off and erratic. They used to never be this way. Just too much of a coincidence with the torque converter unlocking and locking...

Bigbondo007 · May 21, 2013

You guys ever seen an obs jump in and out of OD when the hazard flashers are turned on?

My barn has more horsepower than my truck.

Mark Kovalsky · May 21, 2013

No, I haven't, but I have seen them lock and unlock the torque converter with the hazards on.

Bigbondo007 · May 21, 2013

Yeah, that's what I was getting at. Why you think it's happening

My barn has more horsepower than my truck.

Mark Kovalsky · May 22, 2013

Because of a software fault. It recognizes the hazards as a brake apply, which is supposed to unlock the converter. Later programs had a software change so this didn't happen.

Layson · May 22, 2013

Ok, I disconnected the two front ABS sensors and it still did it. One thing to note that is that it doesn't do it when its cold. Once it warms up it does it. I thought I had it fixed till it warmed up...LOL.

Then I pulled the fuse on the ABS and it still did it. Then I stuck in the new third brake light bulb and it still did it.

Checked all the brake lights and turn signals and they all worked. Now about a month or two the rear passenger door lock actuator is going out. Now today the passenger side front is starting to go out.

Got to do some more digging... I hate electrical issues.

Mark, what does the box do that is connected to the tranny where the main wires plug into. Do those have anything to do with TC lockup?

Mark Kovalsky · May 23, 2013

Box? Got a photo? I don't know what box you're talking about.

Layson · May 23, 2013

Just the little deal below where the shift linkage hooks up. Where the main plug for the tranny plugs in.

Layson · May 24, 2013

Well, I did find one issue with the rear driver side parking light. It wasn't burned out but the filament was broken but would still pass electricity through it. I doubt this was it but you never know...

I was also going to start popping plugs apart and squirting some dielectric grease in them. Then I was also thinking about throwing another PCM in their, I have an extra a NVK3. That should work, right? I think it was out of a late 99.