98 GMC C6500 AUX Brake Light

Discussion in 'Medium-duty Truck Forum' started by leeM, Mar 24, 2014.

  1. leeM

    leeM New Member

    After my truck has been started the AUX Brake light comes on and a constant tone accompanies the light. This light and tone continue while the truck is running and in operation. The brakes seem to operate fine. There is an ABS light on also. The ABS light doesn't go out. The ABS light is on when you start the truck with no tone. Again, after a few seconds the AUX Brake light comes on with a constant tone. Any suggestions to diagnose the problem.
  2. Trevor Roberts

    Trevor Roberts New Member

    My truck is doing the same thing. Have you had any luck repairing it
  3. steven polaski

    steven polaski New Member

    I believe you need to cycle abs system with a code reader that does brakes. You could have a bad abs control module Im working through same issue

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