TPS not reaching to spec
Thread Starter
Teching In
Joined: May 2015
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TPS not reaching to spec So I have done everything I can to adjust this tps to get to .5 and I can only get .75... I have ground down the metal housing, I have ground down the holes on the tps.
Closed all all the way it reads .73, open all the way it will only go to 2.43
i have a Holley efi 95 mm TB on my ls1... please help me :/
Closed all all the way it reads .73, open all the way it will only go to 2.43
i have a Holley efi 95 mm TB on my ls1... please help me :/
It's a simple voltage divider circuit using a potentiometer. If it doesn't produce the desired voltage out then either the 5V reference voltage is off or the resistance values of the pot (tps) are wrong as you turn the tps. The resistance values of R1 and R2 change as the tps is rotated.
Thread Starter
Teching In
Joined: May 2015
Posts: 31
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Okay, I'm not the best with electrical stuff.. but the car runs perfectly fine nothing else is wrong, but it won't idle down it just sits at 2000.. so is it possible that everything else works but it doesn't receive the 5 volts? I have a brand new harness and all new connectors and tps and everything is new
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Verdad Gallardo There are other devises on the 5V Bus that can pull the voltage down so it it is low it could be something other than the tps causing it or it could be the PCM itself which is supplying it. Could be a ground issue too. At this point it's going to take some checking with a volt meter. Without knowing more about the vehicle type or wiring harness (guessing this might be a swap) it's hard to help any more.
Thread Starter
Teching In
Joined: May 2015
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The car I've swapped it into is a Nissan 240sx. The wiring harness is a pre made ls1 to 240sx harness made by wiring specialties. Everything else in the car seems to work fine, it idles and runs fine it just won't go down to 2k and I've checked the idle bleed screw and the throttle position screw on the blade as well. I just tested a different tps and it says the same thing so it has to be a voltage problem going in
Thread Starter
Teching In
Joined: May 2015
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So I did some more investigating... I also tried another tps I know works (came off a working vehicle at my shop) and that one gives me the same results. I measured the input and the voltage reads a constant 4.4v.. the output still only goes to .75
i have a ground from my harness to the head on driver side and from that same spot to the frame rail and another ground on the engine near alternator on block to frame rail as well. I'm lost
i have a ground from my harness to the head on driver side and from that same spot to the frame rail and another ground on the engine near alternator on block to frame rail as well. I'm lost
Staging Lane
Joined: Jan 2017
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First: Verify all PCM grounds are good.
http://www.lt1swap.com/pictures/1_power_ground.gif
With the key on engine off, Unplug the TPS sensor and check for voltage at the plug:
What voltage do you have between wire A on the TPS and wire B?
It should be 5v or very close
Then plug the tps sensor in and with they key on engine off:
What voltage do you have between wire B and C? Does the voltage change at all when you open the throttle?
If you dont get a low to high voltage swing then also check wire C to battery negative and see what voltage you get.
I am assuming the harness was built to LS1 Spec and im referencing this diagram
http://www.lt1swap.com/pictures/9_engine_sensors.gif
If you still have not found the problem, verify that all wires on the TPS ABC go to the correct PCM plug and pin location, 8C1 , 24C2 , 60C1.
http://www.lt1swap.com/pictures/1_power_ground.gif
With the key on engine off, Unplug the TPS sensor and check for voltage at the plug:
What voltage do you have between wire A on the TPS and wire B?
It should be 5v or very close
Then plug the tps sensor in and with they key on engine off:
What voltage do you have between wire B and C? Does the voltage change at all when you open the throttle?
If you dont get a low to high voltage swing then also check wire C to battery negative and see what voltage you get.
I am assuming the harness was built to LS1 Spec and im referencing this diagram
http://www.lt1swap.com/pictures/9_engine_sensors.gif
If you still have not found the problem, verify that all wires on the TPS ABC go to the correct PCM plug and pin location, 8C1 , 24C2 , 60C1.
Staging Lane
Joined: Jan 2017
Posts: 67
Likes: 1
It's in the drawing I linked you to, on the right side it says "throttle posistion sensor" it gives the wire letters, colors, and pcm pin location.
http://www.lt1swap.com/pictures/9_engine_sensors.gif
http://www.lt1swap.com/pictures/9_engine_sensors.gif