Engine/Transmission (1994 - 1998) narrowing this lock-up glitch down - what next?

[VicR]

Ok, I must be getting close - if for no other reason I am simply running out of things it can be (I hope).



The 97 will occasionally flip back and forth between lockup/not locked up when accelerating, most times I can't get it to lock up at all, and sometimes it works just like its supposed to.



Last night I got it to lock up at about 70 MPH, then it acted just like it was supposed to from then on. Turned the truck off and haven't been able to lockup since. I have noticed this before - I can get it to lock at very high speeds then it acts normally for a while. I think there is a clue here, but I don't know what it is?



Its got a new TPS set at . 85 volts, TPS wires removed from the harness all the way back. No codes registered (except 12 and 55). One other thing that may or may not be a factor - yesterday was hot and the transmission temp was over 150 when it started working. Could this be a factor?



What sensor inputs tell the PCM to lock-up? I am going to try cleaning them next. Visual inspection didn't show anything obviously wrong. I wonder if I should check the voltage in the PCM wire back closer to the PCM?



Any other suggestions GREATLY appreciated!



-Vic

 

[Evil Otto]

hey vic i dont know if this will help but my brothers 94 was doing the same thing. it was droping lock up, then stoped lock up all together. so i took to the dealer where i use to work amd used their scaner. i found that it was showing a brake siginal with the brakes not on. i put a new brake light switch on and no problem so far. it locked up good on the ride home. you will need some kind of scanner. i would get a hold of a drb 3 from dodge if you can so you can see all the inputs and out puts to the trans.



good luck

ED

 

[Extreme1]

The brake light switch can cause it, a check would be to see if the cruise works because it would drop the cruise at the same time. The brake light switches on these trucks are adjustable.



Push the brake pedal down with one hand, reach up and pull the plunger out against the brake pedal arm. Release the brakes and you'll hear it ratchet back into place.



Sometimes when you jump out of the truck you can bump the plunger on the switch in too far and it will cause this problem. My tuck had this problem when I bought it 6 years ago, has worked fine since.

 

[A2Z DIESEL]

loc-up search

try grounding pin #11 org/black tracer this is lock up ground control wire if it stays locked then its not likely hydraulic most likely a control input like out put speed sensor solenoid problem pc update etc.

 

[Reddog1]

My son had a similar problem on his '98 12V. Dealer re-flashed his transmission Do-witty (PM Module?) and fixed the problem.



This was the suggestion made by B. K. at DTT, and it worked.





Wayne

 

[VicR]

Good idea on the cruise control. If I can get it to lock up again I'll try the cruise - that might be a easy solution. If not, I guess I'm going to give in and let a professional look at it and see if they can figure it out. Other then this little problem, its a great truck!



-Vic

 

[Bob4x4]

The tps should be 1. 0v at least.



Bob

 

[VicR]

cautiously optimistic

I tightened up the TPS connector and cleaned every other sensor connector I could find on the truck, and I'm cautiously optimistic that I may have solved the problem. Its behaving itself just like it should now. Thanks for the help and suggestions guys! I'll put a few more miles on it tomorrow and make sure, but I think I have this one solved.



-Vic

 

[Dave Remillard]

Vic... Sounds like you've gone through it with this problem. Wondering if you would mind posting the sensors that you cleaned connections on. I've tried pretty much all that you except this idea. Any info would be appreciated. Hope it did fix it for you.

Dave

 

[VicR]

Dave,



I was thinking about it today and if I had it to do over again (or if this darn problem comes back!) I would spend more TLC on the TPS connector. I stumbled onto the fact that the middle wire wasn't very tight in the connector - probably from lots of people pushing paperclips, etc in the back of that socket to set the voltage. I'm 99% sure that wire was my problem. Another thing I was thinking of was making a place to tap the wire close to the firewall and running my digital volt meter into the cab and check voltage while driving. Other than that, I just cleaned everything I could find and access - I'm honestly not sure what they all did.



Good luck - I know how frustrating this problem is.



-Vic

 

[Howard Durand]

Vic,



I think you have a good idea, make up connectors somewhere handy so you can monitor the TPS while under way, or any other time for that matter.

I am not real crazy about shoving test leads into a molded connector to check voltage.

As you already suspect, it could certainly cause damage to the wires or the connector.