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TPS voltage

This is a discussion on TPS voltage within the General Help forums, part of the LSx Technical Help Section category; Originally Posted by transamtom Positive to the yellow,negative to any good ground or back probe the other side. Ok cool ...

  1. #21
    Moderator 98TransAmWs-6's Avatar
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    Quote Originally Posted by transamtom View Post
    Positive to the yellow,negative to any good ground or back probe the other side.
    Ok cool thanks. And I had to order the tps from summit racing who said it might take 3 weeks

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    trying to thread hijack here. Im having a crazy TPS Issue. my car is having bad idle and misfire problem, and so far weve diagnosed it back to the TPS.

    Using a very expensive scan tool. We can view the engine side TPS voltage going crazy.. so the initial thought is the wires from the pcm to the TPS are touching causing the voltage jumps or the pcm is bad..

    then using the scan tool , checked the voltage the transmission is seeing from the TPS, its its good..like .6volts with a linear increase as throttle opens.

    thats leading me to think PCM. im going to check the tps wires for continuety tonight.

    is there something else that could be causing this voltage to be going crazy? i have already swapped the TPS itself, no change.

  3. #23
    Moderator Cutlass's Avatar
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    PCM problems are somewhat rare in comparison to sensors and wiring/connections, but it sounds like you might be on the right track by ruling out the sensor and checking the wiring.
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    So based off of the scan tool showing th tos voltage jumping everywhere. And me probing the wire coming into the ecu, and voltage is correct... Time to order a new ecu.. As the ecu appears to be misinterpreted the data

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    unless anyone has any other ideas?? the scan tool is showing TPS voltage jumping all over the place.. but the actual wire going into the ecu is corrrect steady at .5v at idle , with increase with throttle.

    no other sensors appeared to be going crazy, so i dont think the 5v ref curcuit or ground circuit are compromised.

    i dont understand the internals of the ecu, all i can think is that the ecu is messed up , and interperating the data wrong.

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    Moderator Cutlass's Avatar
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    All you can do is eliminate every other possibility. It's either the sensor, the wiring or the ecm . It's not the sensor.
    If you can rigorously test the wiring, you can rule that out as well. It's three wires. The sensor does not put much amperage load on those wires. But you can load those wires with a light bulb to test them.
    If you are still following me, here is an example of what I mean. The sensor might draw 25 milliamps of current to operate. A light bulb might draw 250 to 1000 milliamps. If you can test all three wires at a higher amperage and the bulb lights up strong...then the wires are fine.
    pajeff02 likes this.

  7. #27
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    Interesting problem... curious as to what the actual issue will turn out to be.

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    well the new ECU changed nothing....

    tonight we are going to hook up a tech two gm scanner to see if that tells us something different than the snap-on scanner we were using.. we are kinda hoping so... but kinda lost as well... my buddy keeps thinking it might be leaking intake gaskets just from his gut feeling as its an air/fuel issue.. although spraying carb cleaner all over the intake had no effect... for $20 i baught a new set of gaskets that i hope to install before we scan it tonight.. maybe we get lucky and his gut is correct.

    but if the gm scanner shows the same voltage problem the snapon one did, then we have no freaking clue what could be doing it , espically since the wire itself is reading correct voltage.and ill be taking it to the stealership to try and figure it out.

  9. #29
    Moderator Cutlass's Avatar
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    Depending on want kind of meter you are using to test the voltage, it could misled you. Cheap meters or even older Fluke meters are very slow. Rapid voltage fluctuations don't get picked up by a slow meter. The meter averages out and displays steady voltage. But the ECM and scanner might be faster.

  10. #30
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    Well the 8k snap on scanner was malfunctioning.. Tps voltage is fine., per the gm tech 2. Smoked the intake and found two leaks. One fixed, other one to be fixed tmr.. Then well see

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