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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?
 

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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.
 

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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.
 

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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.
 

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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
 

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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?
 

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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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2001 Silverado with the auto 4wd. 207k miles.

Sorry to bring up an old subject, but I too have had the dreaded "Service 4wd" message. It seems to be on about 30% of the time...but I haven't had any issues with my system. Few times it felt funny going into 4-low, but that may have been paranoia. Haven't thought much of it till now. Looks like I will be dropping the tranny and transfer case this week to swap in a new tranny. This makes the ideal time to service the 4wd. What do I need to check to make sure the problem is resolved? I read that "LMC Truck sells just the Encoder part", but how do I know that is the problem?
 

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2001 Silverado with the auto 4wd. 207k miles.

Sorry to bring up an old subject, but I too have had the dreaded "Service 4wd" message. It seems to be on about 30% of the time...but I haven't had any issues with my system. Few times it felt funny going into 4-low, but that may have been paranoia. Haven't thought much of it till now. Looks like I will be dropping the tranny and transfer case this week to swap in a new tranny. This makes the ideal time to service the 4wd. What do I need to check to make sure the problem is resolved? I read that "LMC Truck sells just the Encoder part", but how do I know that is the problem?
When my 2000 Silvy (121k miles) was doing this, I replaced the 4wd selector switch and the problem was fixed. It cost me $35 for a new switch. You may want to look into this before forking out the dough for an encoder motor.

Good luck fixing you truck. Let us know how things turn out.
 

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When my 2000 Silvy (121k miles) was doing this, I replaced the 4wd selector switch and the problem was fixed. It cost me $35 for a new switch. You may want to look into this before forking out the dough for an encoder motor.

Good luck fixing you truck. Let us know how things turn out.
I am all for saving some cash here, but I won't have a way of testing the new selector switch until the transfer case and new transmission are back in. How difficult is the encoder motor to change with the transfer case in the truck? Any other things I should watch out for while the transfer case is out?
 

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I had the same issue when I bought the truck, the dealer replaced the actuator. Later the light would still pop on every once in a while. When the service 4x4 light is on my 4x4 selector switch will not work. The light would turn off when I shutoff and restarted the truck. I finally went and had the transmission flushed out and refilled while the truck was running. I'm not sure if the fluid in the transmission has anything to do with the 4x4 system, but I haven't had a service 4x4 light since I had that done.

I also did some reading up on the issue and another common problem was the 4x4 selector switch itself. I also read that it could be a software issue, you might want to call a dealer and see if there is an updated version of the software for your truck's computer.
 
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