Service 4WD Message May be Displayed on Chevrolet Avalanche 1500

The 4WD transfer case encoder motor position sensor or the selector switch may fail causing the service 4WD message to be displayed. Fault code(s) stored in the transfer case control module will be of assistance in determining the exact fault causing the message to be displayed.

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Average mileage: 117,469 (18,400–220,000)
Drive Trains affected: 2WD, 4WD
5 model years affected: 2002, 2003, 2004, 2005, more2006
102 people reported this problem
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problem details
2004 Chevrolet Avalanche 1500 - 4WD 101,365 mi,
Tahoe. No lights on 4wd push buttons, service 4wd in display, both fuses good. No 4wd. just happened so not fixed yet.
2003 Chevrolet Avalanche 1500 - 4WD 131,000 mi,
Drive train jumps from 2 hi to neutral and sometime 4 hi and 4 low. This never happen while driven. Only when you start the vehicle up, you must check the selection.
my service 4 wheel drive indicater is showing on my screen what is the fix for this
2003 Chevrolet Avalanche 1500 - 4WD 160,000 mi,
I had the same problem with the 4 wheel drive transfer acting crazy. Took it to my Chevy dealer and they started exchanging parts with no idea to the problem. It took 4 trips to the dealer until they gave up. It cost me over a grand and I demanded them to fix my truck. I did some research on the internet and found TSB #05-04-21-003C dated Apr. 15, 2008. It instructed the Tech to check the wiring harness from the encoder to the sensor. The wiring harness will short out from moisture and cause false reading to the sensors. I hand delivered this TSB to the Chevy Service Dept and told them to check the wiring harness before they replaced the encoder. I finally got my truck back at 4:00 PM working great. You know and I know, they will never admit to what really took place. So guys check your wiring harness before you start pulling sensors, when your transfer start acting crazy.
2003 Chevrolet Avalanche 1500 - 4WD 101,000 mi,
My 4 wheel drive dont work, the light on the selector is solid on on button but flashes on another, Ive replaced the selector switch and the 4 wheel drive actuator but has not helped.
2003 Chevrolet Avalanche 1500 - 4WD 125,000 mi,
Grinding noise when attempting to use 4WD. Indicator lamp turned yellow and occasionally red.
2005 Chevrolet Avalanche 1500 - 2WD 120,000 mi,
Similar problem, switch fail, but now it's even worse. had my actuator replaced, and the thing went into 4 low by itself then neautral, now only runs but wont move in any gear.
2004 Chevrolet Avalanche 1500 - 4WD 157,000 mi,
When in 2wd while driving will jump into neutral can put in 4wd auto and drives good
2002 Chevrolet Avalanche 1500 - 4WD 140,000 mi,
I had the exact intermittent problem on start up. I took mine to an honest and reliable transmission shop (Terry's Transmission in Syracuse, NY) after I had replaced the selector switch. They determined that it was in the wiring between the selector switch and the encoder motor. They said the encoder was fine. They referred me to a good electric shop, but I did not take it there for the electric repair yet. Likely it is a corroded connection that is "helped" by damper weather since there seems to be at least some correlation with the weather.
sometimes it works ; electric shift, sometimes it doesn't. seems to be affected by slush and cold. sometimes the red neutral light goes on, sometimes the whole thing goes blank. Once I was driving the red neutral light was on and all of a sudden it whacks down into 4 low. Luckily I was just coming ouut of town and not up to speed. When spring hits and I can look at it,I can't get it to do it. Never fixed third winter coming up now.It is getting cold now and it is starting already, red neutral light on. start up truck is in 4x4 without ever selecting it.
I had "service 4wd" message come on an it would go away until I restart truck. There were no diagnostic codes stored anywhere. I did buy 4wd encoder switch and was going to replace it but did not. What I did find is cold solder joints in my 4wd switch on dashboard, the cold solder was not detectable with bear eye I had to use magnifying glass. In any case before you go spend money on encoder switch, take your 4wd switch from dashboard apart and solder all pins of main connector on that board.
2002 Chevrolet Avalanche 1500 - 4WD 160,000 mi,
The vehicle will transfer into 4wd with out being selected.
2004 Chevrolet Avalanche 1500 - 4WD 78,000 mi,
stuck in 4wd auto looking for solution finally took it to a dealer (sorry floks they got you over a barrel the modual shorts out and they have to reprogram it) no they dont carry parts on hand no you cant do it yourself
2003 Chevrolet Avalanche 1500 - 4WD 127,900 mi,
Will not work on 4 hi or 4 low. But Will engage on 4 auto can not figure out the problem
2002 Chevrolet Avalanche 1500 - 4WD 168,000 mi,
Removed xfer case encoder motor after removing plate and pulled front drive. Manually put into 2wd w/drive socket wrench and drove for 5 days before affording part and repair. Total cost under $300.00 including $60.00 for installation by area mechanic. Got most of my info via internet and local Public Library. Ask yours about ENSCO, and you may be able to access Chilton's repair manuels.
2003 Chevrolet Avalanche 1500 - 4WD 188,679 mi,
Won't switch back to 2wd..
2004 Chevrolet Avalanche 1500 - 4WD 44,000 mi,
4W Service message appeared intermittently and would reset after pressing milage button. Re-appear sometimes after minutes and sometimes days..Dealer found the sensor to be bad and replaced $300.
2002 Chevrolet Avalanche 1500 - 4WD 100,000 mi,
started doing funny shifts this past winter n then stopped working completly except i do still have 4 wheel low n 2 wd but no 4wd high or automatic 4wd
2004 Chevrolet Avalanche 1500 - 4WD 94,000 mi,
drivetrain comes out of 2WD for no reason. Usually on start up, indicator will either be 4hi or 4lo or no indication at all. Service 4WD message in dash. Replaced the selector stack. At least get the light show now on start up, but when 4wd selected, won't go into 2wd without turning ignition on and off a couple times. Seems to happen mostly in wet conditions.
2003 Chevrolet Avalanche 1500 - 4WD 118,000 mi,
when starting it switches from 2hi to neutral to 4 hi or low. Only when starting.