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Thread: code P1518

  1. #1
    New Member
    Join Date
    Aug 2018
    Avenel, N.J.
    1997 Silver C5
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    Help code P1518

    while out driving the car suddenly lost power and the message " service traction system" came on. I shut the traction off and the car seemed ok (with check engine light on).
    Got home and ran the OBDII and found code P1518. That code comes up at throttle body problem.

    So anybody have an idea what I'm dealing with?


    '97 C5 \no mods, all stock.
    BUT pretty as hell!
    Last edited by dsimmonds53; 03-14-19 at 10:19 PM.

  2. #2
    Join Date
    May 2010
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    After spending 3 months with the car cranking but not starting replaced the TAC with no change. Checked all wires to TB, PCM, accelerator pedal rheostats, had no change. As a last resort took dash apart and replaced electrical part of the Ignition Switch (lock cylinder and VATS sensor were OK) and car started immediately. Bad contacts can cause low voltage to PCM and TAC and give you a false indication. If this is not the cause and you need a TAC let me know as I have a spare one.

  3. #3
    Technical Writer for Internet & Print Media
    Join Date
    Jan 2001
    CenCoast CA
    71 04 12 19
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    For MY97, DTC P1518 is a fault in the serial data circuit which allows the TAC module and the PCM to communicate.

    The diagnosis of this is fairly complex having 28 steps and requiring a test light, a DMM and the Factory Service Manual.

    The repair will either be replacement of the PCM, replacement of the TAC Module or repair/replacement of all or part of the wiring harness between the two.

    To know what to repair or replace, you need to diagnose the electronic throttle system in accordance with the diagnostic info on P1518 in the service manual.

    A preliminary procedure would be to inspect and clean, if necessary, connections at the throttle body and the TAC Module then road test. If that doesn't change anything then get the FSM, a test light and a DMM and start diagnosing.

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