Service 4wd Light Came On

colrhino · September 22, 2009

Greetings All- a newbie here-

the "Service 4WD" light came on in my 2003 Sierra. the truck has 78k miles on it. I usually do most of the routine servicing myself- is this service just a changing of the fluid in the transfer case? thank you.

bigredmariner · September 22, 2009

It's probably a problem with the shift encoder motor sensor. Some folks have had a problem with cold solder joints in the switch. Look at the pushbutton switch for the 4WD, when you start the truck the switch should blink through all modes and will probably go blank afterwards. This is an indication of a problem in the system and not a reminder to change the oil. Check it out and report back when you can. I would bet that the thing will not go into 4HI or 4LO.

colrhino · September 23, 2009

It's probably a problem with the shift encoder motor sensor. Some folks have had a problem with cold solder joints in the switch. Look at the pushbutton switch for the 4WD, when you start the truck the switch should blink through all modes and will probably go blank afterwards. This is an indication of a problem in the system and not a reminder to change the oil. Check it out and report back when you can. I would bet that the thing will not go into 4HI or 4LO.

actually it worked fine just prior to the light coming on. I was down by the lake (Allatoona, near Atlanta) and had to use the 4wd to get down close to the water to loosen the anchor lines on our water ski jump- after I went back to 2wd is when the light came on, but it seemed like it disengaged like normal.

bigredmariner · September 23, 2009

It's probably a problem with the shift encoder motor sensor. Some folks have had a problem with cold solder joints in the switch. Look at the pushbutton switch for the 4WD, when you start the truck the switch should blink through all modes and will probably go blank afterwards. This is an indication of a problem in the system and not a reminder to change the oil. Check it out and report back when you can. I would bet that the thing will not go into 4HI or 4LO.

actually it worked fine just prior to the light coming on. I was down by the lake (Allatoona, near Atlanta) and had to use the 4wd to get down close to the water to loosen the anchor lines on our water ski jump- after I went back to 2wd is when the light came on, but it seemed like it disengaged like normal.

But will it "still" work now? If it does then I'm not sure what the issue is. But if it doesn't work now then it could be the pushbutton, encoder sensor or a couple of other things.

dakota29 · September 25, 2009

It's probably a problem with the shift encoder motor sensor. Some folks have had a problem with cold solder joints in the switch. Look at the pushbutton switch for the 4WD, when you start the truck the switch should blink through all modes and will probably go blank afterwards. This is an indication of a problem in the system and not a reminder to change the oil. Check it out and report back when you can. I would bet that the thing will not go into 4HI or 4LO.

actually it worked fine just prior to the light coming on. I was down by the lake (Allatoona, near Atlanta) and had to use the 4wd to get down close to the water to loosen the anchor lines on our water ski jump- after I went back to 2wd is when the light came on, but it seemed like it disengaged like normal.

But will it "still" work now? If it does then I'm not sure what the issue is. But if it doesn't work now then it could be the pushbutton, encoder sensor or a couple of other things.

I had the same thing happen all the time... Did the resolder on the switch and still the same thing... After the service 4WD light came on it would lock out all the 4WD controls.. I had to shut down the truck and restart it to be able to use 4WD... At my last oil change I was crawling around under the truck and found the electronic valve that controls the hubs and what not.... Pulled the connectors out of the control module cleaned them with a little contact cleaner and reinstalled the plugs.... I haven't seen the service 4WD service message since... Its been almost 3 months.. Before it would happen about twice a month, sometimes more in the winter when I was using 4WD alot..... Hope this helps, it is worth a try anyway...