Engine/Transmission (1994 - 1998) TPS Adjustment

[Howard Durand]

For TPS problems, go to this web site for cleaning procedures:



http://dieselgiant.com/dodge_diesel_maintenance_tips.htm



For TPS adjustment, Joe G. suggested using a potentiometer in the ground circuit. I decided to try it and It really gives a much better range of adjustment than elongating holes in the TPS body.

Here is a schematic drawing showing how to wire it.

 

[Howard Durand]

Using the above circuit, adjusting the potentiometer adds resistance to the ground leg of the TPS which raises the voltage on the TPS signal wire.

I was able to change that voltage from the stock settilng of 0. 5 volt to 1. 2 and above.

I have it set at 1. 2 at this time and it is working the way I like it.

 

[JFielding]

Tps Cleaning

Thanks again Howard for all your help. I thought it might help some of the other members like me, who are a little nervous about working on the TPS, to hear my experience. Reading the various posts on this issue, I sprayed the TPS while still mounted in the truck. It worked for a day or two at a time. You need to take it off the truck to clean it properly.



Unhook the electrical connector. Remove the two screws with a 7mm socket and the TPS falls off in your hand. I shot a puddle of electrical contact cleaner in the opening at the back of the TPS and moved the actuator with the screwdriver blade on my pocketknife. I heard a grinding sound. The actuator and spring evidently had enough grit in them to cause interference with the action of the TPS. I sprayed the area a few more times and cleaned it out with Q-tips. I then cleaned the pin that the TPS mounts on. Remounting was easy too. Tilt the electrical connector end of the TPS down and it slips right on to the mounting pin. The truck ran great again. I had the thing replaced a couple of years ago by a Dodge dealer. It cost over $200 for parts and labor.

If it ever has to be replaced, it is something that any owner could do in minutes. Its easier than an oil change.

A minor mod, that may stop the problem, will be to fashion a boot over the back of the TPS, to keep the grit out.



I wouldn’t imagine that the TPS wears out internally in a couple of years. Hearing all that grit makes me believe that the problem comes from outside.



It has only been a few days since I cleaned the TPS. The truck is still functioning normally. I will uncross my fingers tomorrow.



I am going to add the potentiometer that Howard has developed and add some test posts as he suggested to me.



Hope this helps.



Joe



94 2500 4x2, Auto. Banks Power Pac, Banks Brake, Twin Ram Intake. Feels like as much power as my 05 2500 4x4 QC short box 6spd.

 

[JPittinger]

Since this is a '94 post, I'm curious what the exact advantages are to adding the pot? I'm guessing (and hoping) that it will effect the shift/lockup points. Anything else? BTW- nice diagram, its nice to read one without squinting.

-JJ

 

[Joe G.]

It does vary the shift/lockup points. It also causes the TCC to stay locked for decelleration until speed has dropped to some point. Not sure of the exact details for that so you will have to wait until Howard gets back on here.

 

[Howard Durand]

JJ,



The primary purpose in adding the potentiometer is to provide a reliable means of adjusting the TPS signal voltage. I have a spare TPS that I was able to make "adjustable" by doing a lot of grinding and filing but when Joe suggested the resistor in the ground leg, I tried that and find that it is so easy and the range of adjustment is much greater.

That said, the primary accomplishment was getting the voltage high enough that the TC stays locked when lifting the foot from the accelerator. I can use the exhaust brake now without manually locking the TC.

It did help in getting the OD and TC shift points higher but there is still the problem of inconsistency. It seems they shift differently depending on how aggressive you accelerate. With light throttle, it shifts much earlier than with heavy throttle.

In a recent post here on this forum I was told that this problem could be corrected with a different PCM. I haven't explored that yet.



Yesterday I unplugged the transmission temperature sender and put in a 5000 ohm resistor. That seems to have a stabilizing effect on the shift points.



This was another suggestion by Joe G. except he uses a 700 ohm resistor.

I may try various sizes to see if it makes any difference.

I am thinking that the value of the resistor doesn't really make that much difference as long as it is constant.



Thanks for the comment on the drawing.

 

[MKline]

Thanks

Thanks Howard, I just got done doing the procedure for TPS adjustment. Everything went exactly how They said it would from dieselgiant. I just took it out for a long test drive and it solved the problem. Last week I didn't know anything about this problem but, thanks to this forum I saved some $$$.



Thanks, Matt