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.Google+
Car Problem Reports
GMC Sierra 1500 4WD Transfer Case Position Sensor/Selector Switch May Fail
GMC Sierra 1500 Problem
Drive Trains Affected: 4WD, Automatic Transmission
Average Mileage: 116,119 mi (29,000 mi - 237,000 mi)
Visitor, 2003 GMC Sierra 1500, 4WD, 125,000 mi
No lights on the selector switch. 4WD wont engage.
Visitor, 2005 GMC Sierra 1500, 4WD, 69,000 mi
Transmission selector button lights on upper left dash are not responding properly. Truck may be in 2WD but indicator lights show 4WD Lo. Sometimes truck will be in 2WD and the indicator light will show neutral or will not light up at all. Sometimes when 4WD Lo is illuminated, the truck feels like it is in overdrive. The first time this happened, a friend told me to disconnect the battery for an hour or so and the problem would resolve itself. It did... 9 months later it is doing it again and the battery disconnect trick no longer works. I am headed to the Dealer tomorrow. Wish me luck!
you can hear the transfer case kickin in, but the front wont lock in. replace the actuator and the switch on the dash and still doesnt work.
Visitor, 2005 GMC Sierra 1500, 4WD, 103,000 mi
service 4wd indicator came on after trouble trying to engage 4wd. 2wd light lit but will not switch to anything else. switch unresponsive
Visitor, 2002 GMC Sierra 1500, 4WD, 235,000 mi
attempted to change into 4 wheel drive low and the front wheels did not lock, lights on push buttons went out also. returned to street and when I try to drive off the vehicle goes into 4 wheel low. no indication from the buttons what gear it is in. no response from pushing any of the buttons.
my service 4wd light came on and i thought i was screwed. the last thing i wanted to do was , take it in and have them tell me i needed $5,000 worth of repairs,.
i looked it up on the internet and it said check the soildering connections on the back of the switch . it said they sometimes werent done correctly and become loose.
and wouldnt u know it , that was the problem . light has never came on since . THANK GOD !!!!!!!!
Visitor, 2005 GMC Sierra 1500, 4WD, 29,000 mi
I had a "Service 4WD" msg pop up out of no where. Looks like it might be the switch based on what I'm reading out here. Wow...quality job #29. What a disappointment! Maybe I'll sell mine & start shopping for a Ford.
Visitor, 2004 GMC Sierra 1500, 4WD, 107,000 mi
Service 4wd light came on. I ignored it for two days and then my 2wd light disapeared and it wouldn't stay in 2wd. I was scared to take it to a dealer and be ripped off, but I was also scared to take it to someone that really didn't know what they were doing and not get the problem fixed properly (especially with it possibly being a transmission issue). I decided to give the dealer here a chance- it was the encoder motor (they looked at the switch first)- $340.41 out the door and they took really good care of me. I think they did a great job and I don't feel like they ripped me off. I do not have the time or the knowledge to replace it myself, and besides this is now warranted by a dealer.
Visitor, 2005 GMC Sierra 1500, 4WD, 108,000 mi
The first indication of a problem I had was driving on the highway in 2wd and encountered icy roads. When I pushed 4wd Hi the truck made some really bad noises and I thought I was going to need to be towed. By the time I slowed down to 30mph I could get the truck back into 2wd and left it there. I did not get a Service 4wd message, so I left it alone for 8 months. Then the problems started...the Service 4wd message came up and I started having erratic issues with the switch. Sometimes it wouldn't light up, would be in neutral or 4-wheel mode and I couldn't get it to go into 2wd, or I'd start the truck and it'd be in 4 Lo and I couldn't corner on dry pavement so I turned the truck off waited for 30 seconds and turned it back on until it finally came out of 4 Lo. A shop replaced the Switch, but the Service 4wd message still came up and the issues with it continued. I took it to another shop who replaced the Encoder Motor, and everything else to do with the 4wd except the computer module. It still didn't work and the codes C027 said the Encoder Motor was still bad, so they put in a second one. Service 4wd message still continued, so I took it to a dealership and they said the 4wd Switch & Encoder Motor needed replaced. I told them I'd just done all that, but they insisted they needed replaced with an $800 quote. I refused service after a $100 diagnostic charge and took it back to the previous shop who replaced the two parts. So far I have not had the Service 4wd message come on again, but it's only been a week. So in summary, I went through two 4wd Switched, 3 Encoder Motors, had wiring redone from the switch to the transfer case & whatever other part replaced on it, the auto-clutches replaced, a left front wheel speed sensor replaced, and fluids changed. The only thing not replaced on the entire electronic 4wd system is the $300 computer module which I was told cannot be Flash re-programmed and can only be replaced if it is bad. In all I'm close to $2,000 in the hole for this issue and I don't feel as if my problems are over. Oh yeah, at one point I had just had a lot of parts replaced and the 4wd switch wouldn't even light up. The mechanic went under the fuse box on the left side of the firewall to wiggle a wiring harness connection and had all kind of codes spitting out, the truck shut off and finally he wiggled it into a sweet spot where the 4wd switch lights came on and everything started working again...of course 2 hours into a road trip the service 4wd message came up while driving in 2wd mode on the highway. The dealership I took the truck to cleaned out the connector and put dielectric grease in the connection because I read somewhere that water from the windshield can get down into the connector and corrode the connection. By the way, I live in New Mexico where it is very dry and there is very little humidity or rain...
Visitor, 2005 GMC Sierra 1500, 4WD, 100,000 mi
This indicator has been on for a few years - I have ignored it because I don't use my four-wheel drive. If I want to put it into 4wd, I put the transmission in neutral before the indicator comes on, push 4wd high or low button, it clunks, I drive around the parking lot, put it back into 2wd and the sensor won't go on again for a few months.