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Service 4wd light

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by kawierider1990, Oct 2, 2011.

  1. kawierider1990

    kawierider1990 New Member

    Alright guys, I was leaving the fair last night and my "service 4wd" light came on in my message center on my dash. While this is on my selector buttons on the left is lit up in 2wd but won't go into anything else. Anyone else had these problems and know of a solution?
  2. rileyjr16

    rileyjr16 Active Member 1000 Posts

    What year truck would help. Mine is a 99 and had to resauter some connections on the circuit board once. It wouldn't go to 2wd. Could also be an actuator.
  3. kawierider1990

    kawierider1990 New Member

    Well I guess that would help Haha its a 2005 z71 with the 5.3 extended cab.
  4. dsfloyd

    dsfloyd New Member ROTM Winner 1000 Posts

    a common problem in that year range was the actuator or encoder motor. I had to do the encoder on mine (it would randomly start up in 4wd). I took it into the dealer to find out as that was more than my scanner would diagnose.
  5. pmf608

    pmf608 Active Member 1000 Posts

    x2 on what david said... that sounds like it is probably the encoder motor(actuator). If that won't move, your truck will stay in the setting it is in. I'd assume it also has some sort of built in circuitry that sets off the service 4WD light when the truck detects that it isnt working.
    Last edited: Oct 3, 2011
  6. adampaul1964

    adampaul1964 Active Member ROTM Winner 1000 Posts

    X3, encoder motor.
  7. Please keep me posted regarding your progress. Feel free to contact me with any questions in the meantime. Thank you.

    Tricia, GM Customer Service.
  8. LS05

    LS05 New Member

    x 4 I get the same message , once in a while the manual says pull over shut off the ignition
    if the message clears on your DIC when you restart the system is okay
    you may try that mine has cleared everytime and I have had no problem going into 4H or Low or back into 2WD
    I have checked the switch on the dash front diff fluid change recently, hasn't done it since I also wiggled the wires on the module
    on the front diff. Dealer wants $200 just to tech 2 scan it. I also found out that LMC Truck sells just the Encoder part seperate from the motor
    which is usually the problem from what I can find
  9. Red Rado

    Red Rado Member

    I just got the dreaded "Service 4WD" message and I can't shift into 4WD Lo. Which I guess is better than being unable to shift out of 4WD Lo. I had this problem once before and they reprogrammed it but ever since then my buttons on my dash have split personality disorder. When I start the truck I have to always check to see what mode it's in or I might be 4WD and not know it. Good info to know that LMC sells just the parts I need instead of getting the whole unit for $200 or more. Any idea if it would need to be reprogrammed after just fixing the encoder part of the motor?
  10. ahm1127

    ahm1127 Member

    Were you able to get it fixed kawierider1990, what was it?

    I know what you mean Red Rado, my 05 Suburban is doing that. Seems worse when cold out, always says 4lo (but not in 4lo) but will switch to neatral after restarting or disconnecting battery, once truck is warm it will show 2high but wont switch to anything else.
    How did yours go?

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