Installing a Potentiometer in place of the TPS
04-27-2010, 11:01 PM
#92
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There are some real treasures out here in these old posts and this is one of them. Tuckerdee's documentation was so good that I didn't even have to look at my truck...I just followed his instructions ...spent $26 on some mini-D connector pins, a 5K linear potentiometer, some shrink tubing, a small 3 wire cable, even mounted it in that slick little panel with a cool **** with a dot on it's top, got it all hooked up, soldered, and shrink wrapped...my transmission can shift very soft and at lower speeds or more firm and higher rpm's for towing. It doesn't take much turning to change the way it shifts. I really love this modification...very slick. Thanks, Tuckerdee. Now on to my Old Smoky Fuel Pin...
07-04-2011, 09:54 AM
#93
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Yes, it works just the same.
Also those of you who want to add a pot and not lose the TPS. Hook some wires to the center wire on the TPS and the ground side(keep TPS connected). Run those inside to the dash. Get a 10K pot and a Diode. It is also a good idea to get a 220uf capacitor. Solder the striped end of the diode to the center post on the pot. Solder the center TPS wire to the free end on the diode. Solder the ground to one of the outside terminals on the pot. This allows you to adjust the TPS and thus lower the shift points and still have the TPS work. The diode is there to keep the voltage from getting too low at idle and throwing a code. The 220uf cap cleans up a bad TPS signal and gets soldered to the two wires from the TPS (+ pos side to the center TPS wire).
Also those of you who want to add a pot and not lose the TPS. Hook some wires to the center wire on the TPS and the ground side(keep TPS connected). Run those inside to the dash. Get a 10K pot and a Diode. It is also a good idea to get a 220uf capacitor. Solder the striped end of the diode to the center post on the pot. Solder the center TPS wire to the free end on the diode. Solder the ground to one of the outside terminals on the pot. This allows you to adjust the TPS and thus lower the shift points and still have the TPS work. The diode is there to keep the voltage from getting too low at idle and throwing a code. The 220uf cap cleans up a bad TPS signal and gets soldered to the two wires from the TPS (+ pos side to the center TPS wire).
I've been trying to figure out why mine isn't working either...
If I read infidel's post right, it sounds like us 96 12v guys have to remove the original TPS completely if we want to rely just on the potentiometer? I know my wiring is good, I've re-wired it once completely, and re-wired the "plug" twice...
07-04-2011, 05:22 PM
#94
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Gen I TPS specs
The bottom line for this mod is that the transmission is looking for specific voltages to respond to. The specs and procedure for the Gen I TBS 1993 D250 Service Manual are as follows:
1. Turn the ignition key to the ON position.
2 Connect the negative probe of the voltmeter to a good ground source such as the negative post of the battery.
3. Probe the throttle position sensor output wire (middle wire) at the TPS electrical connector.
4. With the fuel injection pump throttle lever contacting the low idle speed screw, TPS output should be 1 volt or slightly above.
5. With throttle held in wide open position the TPS output voltage should be 2.25 to 2.75 volts higher than the output voltage is at closed throttle position.
If you are not getting these voltages in your setup you need to modify your resistor. In my setup I completely replaced the TBS with the potentiometer. At 3 o'clock it kicks the tranny out of overdrive, but I can also use the OD kickout button...At 9 o'clock I have a nice low speed soft shift for around town. I used the 5K pot that Tuckerdee mentioned in his instructions on the first page of this blog.
Hope this helps...
Good luck!!
1. Turn the ignition key to the ON position.
2 Connect the negative probe of the voltmeter to a good ground source such as the negative post of the battery.
3. Probe the throttle position sensor output wire (middle wire) at the TPS electrical connector.
4. With the fuel injection pump throttle lever contacting the low idle speed screw, TPS output should be 1 volt or slightly above.
5. With throttle held in wide open position the TPS output voltage should be 2.25 to 2.75 volts higher than the output voltage is at closed throttle position.
If you are not getting these voltages in your setup you need to modify your resistor. In my setup I completely replaced the TBS with the potentiometer. At 3 o'clock it kicks the tranny out of overdrive, but I can also use the OD kickout button...At 9 o'clock I have a nice low speed soft shift for around town. I used the 5K pot that Tuckerdee mentioned in his instructions on the first page of this blog.
Hope this helps...
Good luck!!
10-10-2011, 07:56 PM
#95
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Can someone tell me which is the correct pentiometer ??
271-1720 or 271-1714 ?
One is an audio Pentiometer, and the other is a linear ?
Can't seem to decipher which one is the correct one to use in the sticky ?
Can't see spending $400 (dealer quote for tps) for $ $8.50 worth of parts.
271-1720 or 271-1714 ?
One is an audio Pentiometer, and the other is a linear ?
Can't seem to decipher which one is the correct one to use in the sticky ?
Can't see spending $400 (dealer quote for tps) for $ $8.50 worth of parts.
10-10-2011, 08:15 PM
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10-17-2011, 07:37 PM
#99
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Well,
I bit the bullet for exactly $7.89, as I had the wire already (I used a computer wire that I had left over from an older computer)
I called napa.... $265 for a TPS... Special order only
Dealer $425 for the TPS...
Well.
The $7.89 I paid fixed the TPS and it shifts perfect, stays where I put it and I'm good to go.
Can't believe that an hour of fiddling around, and less that $8 fixed this ....
But it did, and I'm really thankful to all of you guys who are smarter than I who figured this out, so long ago.
Mucho's thankos...
I bit the bullet for exactly $7.89, as I had the wire already (I used a computer wire that I had left over from an older computer)
I called napa.... $265 for a TPS... Special order only
Dealer $425 for the TPS...
Well.
The $7.89 I paid fixed the TPS and it shifts perfect, stays where I put it and I'm good to go.
Can't believe that an hour of fiddling around, and less that $8 fixed this ....
But it did, and I'm really thankful to all of you guys who are smarter than I who figured this out, so long ago.
Mucho's thankos...
01-17-2012, 09:23 PM
#100
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I did potentiometer fix to my truck this past weekend. I was tired of the erratic operation of the TPS, especially when going 75 mph down the interstate and suddenly it drops out of overdrive, revs to 2900+ and slows down to 65 mph before jumping back into overdrive.
I can't believe how well this fix works. I wish I had done this several years ago instead of buying a TPS. I like the way the transmission shifts better this way than with a working TPS, especially when slowing down. Installation was a breeze and only took an hour to complete including soldering the wires to the potentiometer.
I got the potentiometer from our local Radio Shack, part #271-4714 and a ****, part #274-0018, for $5.74 including tax. Picked up some 3 wire cable from Lowe's for a total of about $10 to do this.
Many thanks Tuckerdee for the excellent write up and photos.
Many thanks to everyone on this board that posts so much valuable information, step by step instructions with great photos, and willingness to share their experiences. All have saved me a bunch of time and money, wish I had time to get on the board regularly to help someone else.
THANK YOU EVERYONE!!!
I can't believe how well this fix works. I wish I had done this several years ago instead of buying a TPS. I like the way the transmission shifts better this way than with a working TPS, especially when slowing down. Installation was a breeze and only took an hour to complete including soldering the wires to the potentiometer.
I got the potentiometer from our local Radio Shack, part #271-4714 and a ****, part #274-0018, for $5.74 including tax. Picked up some 3 wire cable from Lowe's for a total of about $10 to do this.
Many thanks Tuckerdee for the excellent write up and photos.
Many thanks to everyone on this board that posts so much valuable information, step by step instructions with great photos, and willingness to share their experiences. All have saved me a bunch of time and money, wish I had time to get on the board regularly to help someone else.
THANK YOU EVERYONE!!!
06-20-2012, 11:25 PM
#101
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There seems to be a bit of mis-leading information as to the correct Radio Shack part-numbers.
Read the post below :
https://www.dieseltruckresource.com/...6&postcount=32
This conflicting information could be cause for some of the mixed results.
05-15-2013, 06:12 PM
#102
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Wiring Question (old thread i know)
I'm hoping someone can help me out here. I have a 4bt with a 47rh(1995) in an 03 F150 Supercrew. I'm using the pcm from the dodge to operate the tranny's OD and LU functions. I have the VSS and tach signal. I have 12volts and ground to my 95 Dodge PCM. the harness I bought was butchered, but I've traced it all back to the connector and know what pins I should be using. Pin 6 is my 5 volt supply- I put a volt meter on it at idle and get 4.97volts. However, I'm also getting 5 volts from pin 4 that goes to the sensor. Pin 22 is a ground that is to go to my VSS (pot replacing it) also and it is 0V so its fine. Am I missing a ground or something that is causing pin 4 to have 4.97 volts to it also? Further, I'm not sure what to do about the OD switch wire. What do I need to do with it to cause the PCM to have the OD ON????? Any help much appreciated.
05-22-2013, 11:38 AM
#103
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I have a 1992 D250 Cummins. I doubt the PCM is working properly. I installed a new trans a few months ago and it worked fine. It stopped charging and I used info from this forum to install an external voltage regulator. About that same time, OD started acting up, it would shift in and out at about 55 MPH. It has gotten progressively worse, the last time i was on the interstate it dropped out of OD several times at about 70 MPH, and the check engine light flickered. It has been on a fair amount recently. I checked the voltage at the TPS and it was low, I shimmed the blade that turns it with pieces of soda can until it was at 1V idle setting. I'm debating using a pressure switch on the governor pressure test port to regulate shifting, or replacing the TPS with a potentiometer. Am I right that a Pot mod will only work if the PCM is working correctly?
05-22-2013, 11:41 AM
#104
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Thread Starter
Check your crank position sensor. If the PCM doesn't see crank movement it shuts everything else down. Mine went bad and acted the same as yours. My clue was that the Tach (factory) dropped out also when this happens. Also killed the CC when it dropped.