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Thread: Tp sensor

  1. #1
    Join Date
    Jun 2002
    Location
    ny\long island
    Posts
    2,724

    Tp sensor

    having problems with my tp sensor. cel came on last week, put my scanner on and code 121 tp low range. thinking ok just replace it. and we good. not.....same code keeps coming up/ idle fine but under load the cel come on and my 93 sc auto stalled, high idle, surges . i have a new tp sensor # th63t . connector looks fine cleaned out tb , maf and still no luck. smh what else do the harness connects to?

  2. #2
    Join Date
    Dec 2007
    Location
    Salem OR
    Posts
    7,143
    Know how to check the ref. & signal volts at the sensor?

    Identify the power, ground and signal wires on the TPS. Do you have an EVTM?

    BK/W - ground/neg.
    O/W - signal
    DG/LG - ref.

    All tests made with the connector firmly seated on the TPS, and key on. DVOM is best. Ability to backprobe at the connector is required. Be careful to not short out while testing...the wiring goes directly to the ECU.

    - Check the reference voltage. This is the voltage running through the circuit between the TPS and the ECU. Touch the negative probe on the DVOM to the negative wire connector, BK/W on the TPS, and the positive probe to the positive/ref, DG/LG. You should see 4.00v~5.00v.

    If the ref. volts are low, inspect the main harness connector behind the pass. side fender well near the self-test connector near the firewall. Open it up and check for corrosion. Still no joy, start checking grounds, look for harness damage, and consider doing voltage drop testing.

    - Check signal voltage. Touch the positive probe to the signal wire and touch the ground probe to the body/engine, etc. Acceptable voltage range is from .49 ~ 1.22 V with the throttle closed.

    Signal volts should change smoothly when the pedal is pushed/released. If the volts jump or don't change, the TPS is faulty, and/or the throttle shaft isn't rotating it correctly for some reason. Confirm the throttle shaft bearings in the throttle body are not worn out.
    Last edited by KMT; 09-08-2019 at 02:05 PM.

  3. #3
    Join Date
    Jun 2002
    Location
    ny\long island
    Posts
    2,724

    Tps

    Quote Originally Posted by KMT View Post
    Know how to check the ref. & signal volts at the sensor?

    Identify the power, ground and signal wires on the TPS. Do you have an EVTM?

    BK/W - ground/neg.
    O/W - signal
    DG/LG - ref.

    All tests made with the connector firmly seated on the TPS, and key on. DVOM is best. Ability to backprobe at the connector is required. Be careful to not short out while testing...the wiring goes directly to the ECU.

    - Check the reference voltage. This is the voltage running through the circuit between the TPS and the ECU. Touch the negative probe on the DVOM to the negative wire connector, BK/W on the TPS, and the positive probe to the positive/ref, DG/LG. You should see 4.00v~5.00v.

    If the ref. volts are low, inspect the main harness connector behind the pass. side fender well near the self-test connector near the firewall. Open it up and check for corrosion. Still no joy, start checking grounds and consider doing voltage drop testing.

    - Check signal voltage. Touch the positive probe to the signal wire and touch the ground probe to the body/engine, etc. Acceptable voltage range is from .49 ~ 1.22 V with the throttle closed.

    Signal volts should change smoothly when the pedal is pushed/released. If the volts jump or don't change, the TPS is faulty, and/or the throttle shaft isn't rotating it correctly for some reason. Confirm the throttle shaft bearings in the throttle body are not worn out.
    thx kmt for the information.

  4. #4
    Join Date
    Jun 2002
    Location
    ny\long island
    Posts
    2,724

    Tps

    I checked wiring from tps on down asfar as i see.i m not to confindent in checking wires that run to main components so i sent it out to a shop i know. A few hrs later a relearn was done, idles fine. I was told the pcm was bad.

  5. #5
    Join Date
    Dec 2007
    Location
    Salem OR
    Posts
    7,143
    Interesting, thanks for the follow up.

    Ken

  6. #6
    Join Date
    Jun 2002
    Location
    ny\long island
    Posts
    2,724

    tp sensor

    well after a pcm from scp , cam po sensor car is running., after 2 weeks and going over post , and help from KMT much thx. #1 cyl is running oil on plugs due to valve seal so i put an extender on it. $300 and she back to normal. now up for sale...i have too many cars lol thx all.

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