I kept getting the same message on my 03 Tahoe. After I replaced the switch, the dealer replaced the encoder motor (not covered by ext. warranty of course). It was about $300 installed. Good luck

 

exactly what i was thinking. I work on these all the time and would put a 100 dollars on it, that it was the encoder motor. not the cheapest part to by in the world but would say that is what it is.

 

had this problem on my 2000 silverado.

put 2 encoder motors in, a dash switch, and a transfer case ecm in and

i found out that the ground's under the driver floor pan, on the outside the frame, that ground the transfer case encoder motor, and the abs unit, were corroded.
this is what kept blowing fuses and eventually destroying the encoder motors.

this is a simple fix, remove grounds, clean frame down to bare metal in that spot, then re-attach ground's.
wola!!!! no more service 4wd, (provided you have a good encoder motor still)

hope this help's other peoplewho have the same problem, i know i spent 3 hours reading post's on this issue.

enjoy!!

sy0569

 

Sometimes when it is cold outside, I can get in and start it and the truck will drive but the switches say that it is in Neutral. Push 2WD and it flashes right back to it. My Service 4X4 comes on a lot too after it has sat all night and I drive for a couple of miles, while I'm rolling I just put the trans in neutral and turn the truck off and start it right back up and dont see the light for a month or so.

 

could also be the ground wires on the drivers side on the frame, my 4wd light came on and the grounds were corroded real bad

 

Well I know I have replied to this before but now I think I have problems. Just now heading home I started the truck and it showed it was in 4 low, I pushed the 2wd button and all it did was flash. I back out of my grandparents driveway to tow my bro home and the front diff was not ingauged (turned without the drag). While towing him home it was still in 4low and I was rolling at about 18 mph and it started jumping and trying to die in the throttle but when I let off it went back to smooth idle. I made it home, only 3 blocks, and turned the truck off, went inside for 5 min and got back in it. When I started it, it was now in 2wd and everything was fine. My service 4X4 light has been coming on and off a lot lately but like you all said it might just be the switch so I have been ignoring it. Does anyone have any idea what kind of trouble I am in now??? Thanks, Ryan

 

i have found the solution to all of this....go to your local auto parts store, buy a 18"-24" battery cable with eyelets on both ends. take one bolt out of the transfercase encoder motor, then put 1 end of the cable on the bolt,...tighten.

next find an existing bolt, or stud on the frame, remove bolt/stud, take a grinder, and clean the frame down to bare metal around the hole/stud. put the other end of the cable on here, tighten.....wola!!! now your encoder motor has a proper ground of a proper size.....overkill!!!
never have a problem agian!!!

 

What are you gonna say when your Encoder motor sensor inside the encoder moter goes bad, like they do all too often, and then your Service 4WD System lights up again?

Here comes your problem back again.

Boyz, it's not always the damn grounds. The Encoder motor goes bad on these truck alot because of the sensor. Then we all know we have shitty selector switches on the dash too. So examine all the wek points before you dedicate yourself to a single repair that may or may not work.

 

ok let me re-phraise.....it worked for me, and it can't hurt to have a better grounding system.

 

Common problem that causes it (sorry if someone else mentioned... don't have time to read it all ATM) is the solenoid (iirc in the front diffy) going. Cheap part, expensive as **** labor to fix it.

EDIT> and btw, they're all correct about the motors (and solenoids also do) dying alot, happens in testing all the time.