Archived Erratic T/C and O/D operation

[ronco]

Was on the way home this afternoon (far from home) when I felt the trans. downshift out of O/D. I have had to clean the TPS before and thought this was the same problem. At this time, I was still 250 miles from home. I go off the interstate at the next exit, removed the TPS and sprayed contact cleaner into the input shaft. Rotated shaft with screwdriver a few minutes and installed. Checked voltage at idle and adjusted to 950 millivolts. Used digital meter and watched bar graph while I operated throttle from idle to wide open. No obvious "dead spots" in sensor. Got on interstate and still did not have O/D. Ran home at around 2500 R. P. M. all day. When I next got off the interstate, trans would shift into O/D during decel at slower speeds >60 M. P. H.

On highway near home in slower traffic, O/D came back, but had no T/C lockup. T/C locked and unlocked on interstate at 25-2700 R. P. M. Stopped at store to pickup groceries and still got O/D at low speeds and low throttle pressure, but no T/C lockup.



I will clean the T. P. S. again, but I wonder about the trans. temp sensor. What value should it read in ohms when at temp? I checked fluid in driveway for smell and color. Looked right and smelled normal, also, felt cool to the touch.



I need to load my truck Wednesday for an 800 mile trip North. Any and all help appreciated. I have a factory manual if someone knows the pages for diagnosis of my problem. Thanks!



Ronco

 

[VicR]

check the connector

I fought an intermittent lock-up problem for a few weeks. Turned out to be a loose wire (middle one) in the TPS connector.



Also, a lot of people have had success seperating the TPS wires from the wire bundle all the way from the TPS to the firewall, but as you have a new problem I doubt this would be your solution - but its a free fix.



Before I found this loose wire, I was going to tap the middle TPS wire so that I could monitor actual voltage while driving. That might give a clue as to what is actually happing.



You might want to put in a mystery switch if you don't have one already. If you get into a situation where its hunting between lock/unlock, you can overheat a transmission. A mytery switch to unlock the transmission (and transmission temp guage) can help you limp home.



-Vic

 

[illflem]

The trans temp sensor should read around 700 ohms at normal operating temperature.

You can jump across the sensor connector with a 700 ohm resistor to isolate the problem.

 

[ronco]

Gentlemen, thanks for your replies. I took the truck to a local mechanic with a scanner. He told me the T. P. S. sent a trouble code three times and I had a code stating the batteries had been disconnected. So, I will install a fresh T. P. S. on Monday and ride on. BTW, does anyone know the part number from Cummins for the sensor? I spoke to a Cummins parts rep. today on the phone and gave him the engine serial number and was told this is a Dodge part only. I would have swarn that I read here that the part can be purchased at Cummins. Thanks.







Ronco

 

[VicR]

I've got a 97 so the TPS is probably a different number then your 95, but I most certainly did get it at Cummins in a Cummins box at about 1/2 of what my friendly local dealer wanted.



I now carry my old one in the truck as an insurance policy. My wife has the truck out now but PM me tomorrow and I'll get the p/n off the box if you want it.

 

[Andy Redmond]

Good luck, I'm betting both have been superceded several times.



These numbers were derrived from a 96, auto trans 2x4's engine serial no.





Cummins # Dodge #

3930318 4874412

 

[ronco]

Andy, after searching old posts for around an hour, I found the same numbers you listed as well as a NAPA number. Thanks to all for your help and suggestions.





Ronco