Cleaned throttle body idle issue.

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by EricS1, Jan 23, 2013.

  1. EricS1

    EricS1 New Member

    Cleaned my throttle body on my 2008 silverado 5.3l and idling a little off. Seems to be too high, anyone know should I take to dealer to recalibrate or is there another option? I decided to clean after check engine came on and code p0121 was reading on diagnostics.
  2. Enkeiavalanche

    Enkeiavalanche Loving the Outdoors Staff Member 5+ Years ROTM Winner 5000 Posts

    Sounds like a Job for Seafoam...
  3. j cat

    j cat Epic Member 5+ Years 1000 Posts

    what product did you use to clean ? high idle would indicate a air leak/vac leak.

    the 121 means the MAP and the TPS are out of wack. not within the programed operation. usually a leak.
  4. pmf608

    pmf608 Epic Member 5+ Years 1000 Posts

    This is a problem we always had with the computer-controlled throttle bodies on these new trucks when I was doing my work study at my local GM dealer. As the gunk builds up inside the throttle body, the computer slowly adjusts the idle position of the throttle body to account for it and regulate the air flow at idle. The problem is, when you clean the throttle body and the gunk is suddenly gone, the computer thinks that the sudden change is an incorrect reading and doesn't compensate for that. We would always have to use the Tech 2 to reset the throttle body position whenever we cleaned a throttle body. You could try driving it long enough to adjust itself back, or disconnecting the battery for long enough for the computer to drain all of its residual power and reset, but neither of those is guaranteed to reset the throttle body position.

    The only way that I know 100% works is to use the Tech 2 to do a relearn of the throttle body position sensor so that the computer will put the throttle body back at its normal idle position.
  5. TRPLXL2

    TRPLXL2 Epic Member 5+ Years 1000 Posts

    This why I like the pre 98 vehicles, TPS can be reset by holding the gas pedal 3/4 way down and starting the vehicle and letting off the gas and shutting the vehicle off. BAM!! Tps reset lol!!!

    Good luck with your issue!!

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