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  1. #1

    Default Service 4wd light

    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. #2


    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.

    If at first you don't succeed, get a bigger cheater bar.

    1999 GMC Sierra SLT Z71 | 5.3 "Vortec" | Spectre "Cold Air Intake" | TransDapt TBS | Hypertech 30005 Tune | 2005 Chevy Tail Lights | Denali headlights | Grill Mounted Fog Lights | AWS Bug Shield | 265/70/16 Futura Scramblers | Boss HD Speakers | 2005 Overhead Console | Flowmaster Super 40 mufflers 2N1O | Mostly stock-ish
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  3. #3


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

  4. #4


    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.
    2004 Silverado 2500 Crew Cab 4x4, AMSOIL EA air filter, Granatelli MAF sensor, Throttle body spacer, Magnaflow exhaust (true dual to 2 in 1 out muffler), 6" ProComp lift (add a leaf and 5" superlift rear block), Bilstein shocks, 35's (Cooper Disoverer ST) and 4.10 gears, Rhino Liner, EGRUSA fender Flares and widow visors, extended stainless steel brake lines, firestone airbags w/onboard air compressor, Pioneer Avic X940BT navigation, Accel backup camera.
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  5. #5


    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 by pmf608; 10-03-2011 at 01:41 PM.

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  6. #6

  7. #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. #8
    Jr. Apprentice LS05's Avatar
    Join Date
    Nov 2010


    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
    2005 silverado K1500 Z71
    2001 Blazer LT 4x4
    2000 Yamaha Wolverine 4x4
    1995 Jeep Grande Cherokee(got rid of that piece of crap thank God!)
    1993 Ford Exploder (wish it did explode would have been easier than fixing it all the time!)

  9. #9
    Sr. Apprentice
    Join Date
    Jan 2008
    Taneytown, MD


    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. #10
    Sr. Engineer ahm1127's Avatar
    Join Date
    Jan 2009
    Pennsylvania, United States


    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?
    Everyday I wake up is a great day! ;-)
    05' Chevy Suburban, 11' Ford Fiesta

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