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How do I test for a bad TPS? searched but...

Discussion in 'The Garage' started by tx_sub, Nov 19, 2004.

  1. tx_sub

    tx_sub 1/2 ton status

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    tried the search but gave up.

    how do i test to see if my tps is functioning properly? i'm trying to chase down my rough idle problem and all help is greatly appreciated.

    /forums/images/graemlins/burb.gif /forums/images/graemlins/thinking.gif
     
  2. tx_sub

    tx_sub 1/2 ton status

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    no codes. egr moves without binding, and changes idle when depressed.
     
  3. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    Backprobe the sensor at the signal wire. It should be .5V closed, and 4.5v open.
     
  4. tx_sub

    tx_sub 1/2 ton status

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    with the engine running? or off or ingnition in on position?

    and could it be bad and not throw a code?
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    You can test it with engine off, key on.

    It needs to be smooth too, the voltage should change as throttle position does.
     
  6. tx_sub

    tx_sub 1/2 ton status

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    thanks

    but i still would like to know if it could be bad and NOT throw a code?
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Yes, it can, since the ECM interprets TPS voltage as a percentage of throttle opening. The ECM can't tell that you aren't holding the pedal down (for instance) when it is seeing voltage that indicates WOT, if that makes any sense.

    It can be outside of the base range of voltage and I don't believe you will see any codes. Again, it comes back to the fact that the ECM doesn't really know how far your foot is depressing the pedal, if at all.
     
  8. Triaged

    Triaged 1/2 ton status

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    You need to get a cheep analog (not digital) volt meter. Hook it up to the TPS and measure the resistance as you open the throttle. The analog meter will pick up "blips" that you would miss with a digital meter. It needs to be smooth.
     

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