I know I've seen something along these lines here before, but I cant seem to think of the right search.

long trip, overdrive starts downshifting arbitrarily, gradually gets worse.

pushing on overdrive button to isolate only results in a sporadic light in the center of the button... o/d continues to engage and disengage.

I crawl under the truck (450 miles from home and still 100 miles to go) and remove and check all the electrical connectors from trans etc.

eventually, will not engage at all. voltmeter starts to read low, cold start and water in fuel lights blink sporadically, as well as a small light between the voltmeter and the temperature gauge.

I know this is a common problem, just cant seem to find the thread.

tks,
rjm

 

Sounds like the PCM is unhappy. Unplug the PCM and check the connector for crud first.

 

I crawled under the hood and wiggled any connectors I could find. the problem seems to have gone away for now.

Its amazing the extent that a minor short or corroded terminal can cause such widespread system failures.

I'm guessing it could be a real nightmare trying to transplant these electronic dependent motors into something not even close to what they were intended for.

oh well, at least I'm back up and running in overdrive again.

tks,
rjm

 

I had a similar problem with my '93 cummins. after hearing much crap from tranny rebuilders I was told it was my TPS switch.(by an HONEST tranny guy.) He told me to remove and clean the sender unit located on the engine. I did, it worked. Now I just clean it once every 6 months or so... Hope this helps.

 

My 93' was doing the same thing. I found out it was the TPS switch, which is located right on top of the pump. After finding out the only place I could get a new one from was dodge, for $325, I tried to find a way to fix it. The problem is after a while they start to wear out and it sends incorrect voltage readings, usually the voltage readings drop. I fixed mine by plugging my scan tool in to the truck, unbolting the TPS from the pump and rotating it clockwise (increasing the voltage readings) until I got the voltage to read within the required range. I think it was something like .08 to 1.2 at idle, and 3.2 to 4.0 at WOT. Then I marked and drilled new mounting holes through the bracket and bolted the TPS back on. So far it has been working great. Hopefully this makes sense, if I can clear anything up for you let me know.

 

Bar, were you aware there is an adjustment on teh TPS for seting teh voltage? requires a multimeter and a 10mm wrench...

 

Is it the trans temp switch? If the fluid cools too much it will kick out.
I'm not sure about the 93 model years.
My 94 did the same and all I had to do was cover the radiator with a towel with it running. It would stay in place until I shut it off.

 

my truck the brake light and the abs light will come on and go out some times blink and some times be very dull whay would cause that