Throttle Position Sensor Misadjusted
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HT4100 4.1, 4.5, 4.9 Discussion, Throttle Position Sensor Misadjusted in Cadillac Engine Technical Discussion; Folks: I hava stubborn Code E055 (Throttle Position Sensor Misadjusted). I have checked to make sure no cables are binding ...
  1. #1
    EldoRedo's Avatar
    EldoRedo is offline Cadillac Owners Fanatic
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    Throttle Position Sensor Misadjusted

    Folks:

    I hava stubborn Code E055 (Throttle Position Sensor Misadjusted). I have checked to make sure no cables are binding the throttle lever, but I'm not experienced enough to perform more sophisticated diagnostics the service manual describes.

    The car seems to run fine -- is this something serious enough to worry about? I ask because if so, I'm concerned my dealer will use it as the latest opportunity to overcharge me -- so the second part of the question is, is this something a smaller independent shop could typically be expected to remedy?

    Thanks.

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    awadecki is offline Cadillac Owners Enthusiast
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    Re: Throttle Position Sensor Misadjusted

    Well, yes and no. This isn't a hard job to do yourself. My guess is that someone previously installed a new sensor and failed to calibrate it (typical of the smaller shops, although dealers should know what they're doing). Here's what you should check:

    First, get your car up to full operating temperature. Then, disconnect your ISC motor and move it away from the throttle body so that it doesn't hit the throttle actuator (on my 4.1 there are 3 nuts you take off, I can't remember how my 91 worked, but it's probably similar).

    Push the throttle forward and let it snap back. You are now at your min. air setting. Start the car and enter diagnostics and read the RPM parameter (can't remember what it is for the 4.9 cars, P.0.8?). It should be around 450rpms. If not, adjust the throttle stop screw with a torx wrench (size T-20 I believe--buy an offset torque wrench from the auto parts store) to attain this RPMs.

    Once you've established min. air. Shut the car off. Check parameter P.0.1. It should read 0. Yours likely reads -1 or +1 or somewhere thereabouts. Unscrew the two torx bolts at the throttle position sensor enough so that you can move the sensor around. Move it until parameter P.0.1 reads 0. Then retighten the screws. Check again to make sure that P.0.1 reads 0. Now reconnect the ISC. You should be all set. If you want to be more precise, set your TPS voltage to 0.5V at min. air using back probes.

  4. #3
    EldoRedo's Avatar
    EldoRedo is offline Cadillac Owners Fanatic
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    Re: Throttle Position Sensor Misadjusted

    Excellent -- thanks!!

  5. #4
    awadecki is offline Cadillac Owners Enthusiast
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    Re: Throttle Position Sensor Misadjusted

    On the 4.9, you can also trick the ISC to retract by holding the throttle with your hand and pushing on the plunger with your finger. It'll retract fully at which point you can disconnect it.

  6. #5
    peteski is offline Cadillac Owners Enthusiast
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    Re: Throttle Position Sensor Misadjusted

    The "finger method" ISC plunger retrection works just as well on the 4.1 engines.
    As long as you pull the throttle a bit to rev up the engine while holding the plunger in. That keeps the throttle switch closed telling the ECM that the throttle lever rests against the plunger. The ECM will retract the plunger trying to reduce the rpms.

    Peteski

  7. #6
    zentrade is offline Cadillac Owners Fanatic
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    Re: Throttle Position Sensor Misadjusted

    Ok here is my dumb question. Where is the throttle stop screw? (to adjust idle) Thanks!

    Quote Originally Posted by awadecki View Post
    Well, yes and no. This isn't a hard job to do yourself. My guess is that someone previously installed a new sensor and failed to calibrate it (typical of the smaller shops, although dealers should know what they're doing). Here's what you should check:

    First, get your car up to full operating temperature. Then, disconnect your ISC motor and move it away from the throttle body so that it doesn't hit the throttle actuator (on my 4.1 there are 3 nuts you take off, I can't remember how my 91 worked, but it's probably similar).

    Push the throttle forward and let it snap back. You are now at your min. air setting. Start the car and enter diagnostics and read the RPM parameter (can't remember what it is for the 4.9 cars, P.0.8?). It should be around 450rpms. If not, adjust the throttle stop screw with a torx wrench (size T-20 I believe--buy an offset torque wrench from the auto parts store) to attain this RPMs.

    Once you've established min. air. Shut the car off. Check parameter P.0.1. It should read 0. Yours likely reads -1 or +1 or somewhere thereabouts. Unscrew the two torx bolts at the throttle position sensor enough so that you can move the sensor around. Move it until parameter P.0.1 reads 0. Then retighten the screws. Check again to make sure that P.0.1 reads 0. Now reconnect the ISC. You should be all set. If you want to be more precise, set your TPS voltage to 0.5V at min. air using back probes.

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