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Thread: engine surge- throttle warning light

  1. #1
    Join Date
    May 2011
    Location
    linwood,nc
    Posts
    56

    Default engine surge- throttle warning light

    hey everyone i hope someone can help me. i have a 98 chevy k3500
    4x4 auto tranny 6.5 turbo diesel. my engine speeded up all of a sudden
    for no reason. i got home and a light on the dash came on that said
    service throttle soon. do i replace accelerator pedal module or
    throttle position sensor. where is the throttle position sensor located.

    thanks for any help

    steve n.carolina

  2. #2
    Join Date
    Apr 2001
    Location
    CA
    Posts
    13,573

    Arrow

    The APP (pedal module) is the throttle position sensor. There are no other "throttle position sensors". The pump is electronic, with all moving parts internal.

    Check the connectors and harness before anything else. The "Service Throttle Soon" indicates a loss of communication with the APP, or input values out of spec. If this is the first time you've seen this lamp, and you have immediate issues (engine surge w/ the lamp), a connection problem is likely. Try cleaning the contacts and reconnecting the connector.

    The APP module has 3 internal independent circuits, and 3 stages of fault:

    Lose 1 circuit = STS lamp only, and possible delayed or unusual throttle response;
    Lose 2 circuits = STS lamp and limp mode;
    Lose all 3 circuits = STS lamp and no throttle response.

    If the APP module is at fault, don't try to repair it, unless absolutely necessary. There are methods of "cleaning", which often result in a functional APP, but this should be considered a temporary repair, and unreliable. The APP's are extremely reliable (normally), so a used replacement (vs. new) is not a bad idea, and a lot less expensive.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  3. #3
    Join Date
    May 2011
    Location
    linwood,nc
    Posts
    56

    Default thanks very much

    i really needed the help here. im new to chevy diesel.

    thanks a bunch have a great day

    steve n.carolina

  4. #4

    Default

    Quote Originally Posted by DmaxMaverick View Post
    The APP (pedal module) is the throttle position sensor. There are no other "throttle position sensors". The pump is electronic, with all moving parts internal.

    Check the connectors and harness before anything else. The "Service Throttle Soon" indicates a loss of communication with the APP, or input values out of spec. If this is the first time you've seen this lamp, and you have immediate issues (engine surge w/ the lamp), a connection problem is likely. Try cleaning the contacts and reconnecting the connector.

    The APP module has 3 internal independent circuits, and 3 stages of fault:

    Lose 1 circuit = STS lamp only, and possible delayed or unusual throttle response;
    Lose 2 circuits = STS lamp and limp mode;
    Lose all 3 circuits = STS lamp and no throttle response.

    If the APP module is at fault, don't try to repair it, unless absolutely necessary. There are methods of "cleaning", which often result in a functional APP, but this should be considered a temporary repair, and unreliable. The APP's are extremely reliable (normally), so a used replacement (vs. new) is not a bad idea, and a lot less expensive.
    My son just had this happen to him yesterday. He had to go about 10 miles at idle to get it home. The STS light came on but it did not throw any codes. I hopped in it today and everything worked fine. Should I clean the connections at the pedal? Are there other connections in the harness I should check?

    Thanks.
    98 3500 GMC 4X4 crew cab Auto SRW

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