1999 chevy 2500 4wd problems no power to wheels

Discussion in 'GM Powertrain' started by losethetail, Jun 17, 2009.

  1. losethetail

    losethetail New Member

    I have a 1999 silverado 2500, not sure which transfer case as of yet. It has push button 4wd drive. I click into 4hi and 4lo, and i can hear the transfer case shift. when i drive in 4lo, i can definitly tell that i'm engaged into 4lo. however i have no power at the front wheels.
    I have no lights for service 4wd on the dash

    I can do mostly all mechanical work, just trying to find someone that ran into this before. any help would help.
  2. Bikeman

    Bikeman Member

    first check your 4wd fuse in the left fuse box, I think located on the left side of the dash behind the close out panel. If blown replace and see what happens, could be a short.

    Otherwise hard to say, the is an electric motor acuator the egages/disegages the front axle. It is controlled by the tranfer case control module. Looks like it has 4 wires going to it.

    Theres a brown wire which is b+ from the 4wd fuse
    A black wire which is ground.
    Disconnect the connector from the motor, located kind off on top of the front diff. Check those for ground and power with the igniton on. If you get 12 voltz power and ground are good. If no voltz check those circuits for opens.

    If they are good, its going to be hard to further diagnose with out a tech 2 scan tool.
    The grey and black wire on the motor connector is from the transfer case control module and when acuated its grounded. Th other wire is feed back to the transfer cas control module to tell it whether the front diff is engaged or not.

    You are probably looked at needing the acutating motor or the atc (transfer case control module).

    Do you have the resources to retrive trouble codes from your truck?
    1 person likes this.
  3. daddytech

    daddytech Epic Member 5+ Years 500 Posts

    wow bikeman covered my usual easy stuff to check, Fuses and the computer codes.

    I am really impressed with all of the knowlege about the wires and such, never seen anyone go into that kind of detail before. Nice job

    be sure to post the resolution on this thread so that every one else can benefit from your experience please.
  4. Bikeman

    Bikeman Member

    uhm, yeah, when its slow at work, I read these and then search the gm service database for bulletons and info. I don't know the answers but I know where to look for them;)
  5. Springthing

    Springthing Epic Member 5+ Years 1000 Posts

    Well, I'm one of the ones that's kind of hoping work stays slow often for you... lol
  6. yotchie

    yotchie Rockstar 100 Posts

    thats the same prob i had in my 89. and it was the actuator on the front diff. deffinately give that a good check
  7. Jimmiee

    Jimmiee Epic Member 5+ Years 1000 Posts

    If you get your truck scanned you will know where to start looking for the problem. More than likely it's the actuator but we just had a truck not too long ago where the front drive shaft broke and was spinning at the plunge joint.

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