LS240_sx

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 :/

2xLS1

iTrader: (25)

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.

LS240_sx

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

G Atsma

What he is saying is, to simplify, either the input voltage is more or less than 5 volts, or the sensor itself is bad, even if new(it happens.....)

LS240_sx

How would I measure the input voltage? Ground with the black and measure off the grey wire? I have a 3 prong grey blue black wire.. sorry for all the stupid questions lol

a05c

Which sensor is it (Model/manufacturer)?

is it a 3 wire sensor?

LS240_sx

Ac delco 3 wire

LS240_sx

https://m.summitracing.com/parts/ado-213-912

a05c

Do you have access to a wiring diagram or can post a picture of the diagram?

I'm thinking it's looking for a 0-1v signal, it might not have a 5v reference signal.

2xLS1

iTrader: (25)

Drive by cable 3 wire tps uses 5V reference.

a05c

I'm used to working with stuff that is super low voltage. Milli and micro voltages. You're probably right. I was thinking about it more and it makes more sense.

2xLS1

iTrader: (25)

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.

LS240_sx

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

LS240_sx

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

LS240_sx

Anyone? It's not getting 5 volts the Harness is grounded to driver side head and from that same spot the engine is grounded to the chassis

Compsystems

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.

LS240_sx

Could you tell me which wire is A b and c? I'll look at all of this thank u so much

Compsystems

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

LS240_sx

Okay thank you. I'm going on a vacation this weekend but I'll be able to work on the vehicle next week and I will post what results I got