I checked my TPS voltage because the OD is not shifting right and because the error code I get is 24. I found the voltage, at idle is 4.8 V :-[ , the Voltage at WOT is at about 2.8 V I am reading the voltage from the Ground(black wire) to the center (orange wire) As you all now this is not what the TPS should read. <br><br>To give you history of my truck, I have a 94 engine (with p7100 IP) in my 1992 truck. My tranny is stock automatic with not added shift kits etc.<br><br>I need someone to check there 94-98.5 service manual and tell me if the plug into the TPS (looking down from the top) has the wires from left to right in the order of Black, orange, white/purple or ground, center, 5 V? <br><br>The only thing I can think is the wires, ground and hot, are switch between model years. This is the only way the TPS could read from high to low voltage, as you throttle it up.<br><br>Thanks in advance for any suggestions or ideas, I checked out on http://www.dieseltrans.com and did not find any help there.

 

This is what I have found. On my way home from work yesterday I stopped at a used truck place and crawled around a 95 CTD truck long enough to verify that the ground and hot wires on the TPS connecter are swapped. Let this be a lesson to anyone putting a 94 - 98.5 engine in a 89 to 93 truck.

I went home and swapped the two wires and checked the voltage. The voltage at idle was about .4 volts. Because I knew the adjustment needed to get the voltage with-in the 1.2 to 1.5 volt range was to great for the amount of adjustment play in the TPS, I added a Pot (potentiometer), this worked great because I can get any range of voltage I want, and I can change it with only a turn of a screw. I took it on a test drive, after about 3 stops to fine-tune it, I have my OD shifting just where I want it. After I drive it for a while I may replace the pot with a fixed resister

Now I am a very happy camper, my error code is gone, my OD shifts great and the hole truck/ tranny experience seams to be much better. ;D 8)

 

Where do you wire the potentiometer into? I checked my TPS and at idle setting was 0.4 V and am having trouble ramping it up to the 1.2 with positioning alone. Got it to .7 V but it doesn't make much difference. Thanks.<br><br>Paul

 

I put a 10K ohms pot on the black Ground wire. I would have used a smaller pot if I had one. I measured the pot resistance to be about 800 ohms when the voltage was set to 1.4 Volts (from black to orange wire, including pot). Yours may be different depending on the TPS resistance and what the voltage is now. I did not have time to check the ohms across the pot after I made some fine-tuning adjustments. I will check it tonight and let you know. <br><br>Feel free to email me if you have any questions.<br>Howard

 

I just did an end result check on voltage and resistance. I set the TPS voltage to be 1.5 Volts, the pot resistance is 880 ohms. My OD is shifting at about 30 to 35 MPH. My question for all you with auto trannys at what speed should I have my tranny shifting to OD? When I set my OD, to shifting at 45 MPH my TPS voltage is 2.5 volts at idle. What should I set it at, or is it just personal preference?

 

Howard,
I think you have the best answer for the 91-93 auto using a pot. Did you put the pot on the dash so you could adjust the shift point in the cab? I have had mine at a fixed voltage of 1.3 volts for an upshift at 37 mph. Sure reduces the needless shifting on mountain roads. My tranny has lasted 240,000 km and twelve years so far.

 

Now that's a good idea for anyone that does a lot of different kinds of driving. I wish I had thought of it