4 WD service light

bbviper · February 8, 2003

I just bought a 200 GMC Sierra w/ 38000 miles. THis morning the four wheel drive service light stayed on when i started my truck. Last night, I was driving it in 4 hi because the roads were icy. Now it is stuck in 2 wheel drive and I cant switch it to anything else. Any ideas. My truck also has the annoying clunking sound when I stop and go again. Whats the latest on remedying this problem. THis site is so cool and informational. I am glad to be a part of it.

dsmazz · February 8, 2003

Sounds like the servo motor that transfers the gear set (if you have AutoTrac pushbuttons on the dash), has failed. If that's the case, get ready to spend some major $$$. If yours is a manual transfer case, something inside the transfer case has jammed. My wife's 2000 Sonoma had the servo motor fail three times (under warranty).

bbviper · February 8, 2003

I have the pushbutton model. I was told that it might just be the transfer case switch.

dsmazz · February 8, 2003

It could be, but usually if it is the switch you won't get the message center indicating a problem with the 4x4. GM had a high failure rate on some servos for 2000 models built in late '99.

lrymal · February 8, 2003

... THis morning the four wheel drive service light stayed on when i started my truck.

I had the 4WD module to fail only a few days after I purchased my new 03 Silverado. Initially, the dealer said the switch assembly was defective but that wasn't the problem. He then thought it was the motor in the transfer case, but that wasn't it. They found it to be the 4WD computer module, which sits under the dash, left of the steering wheel shaft.

It is part of the brain of the thing and rarely goes out. Note that my symptoms were the "SERVICE 4WD" warning, and no pilot lights would illuminate on the switch assembly.

bbviper · February 8, 2003

I also have no pilot lights on any of my switches either. And I cant put the truck into 4wd. Maybe thats it. I have no warranty left. Whats the cost. Also being that my light is on, can they get a code from the 4wd service light?

lrymal · February 9, 2003

First off, look at how my dealer approached this. He thought it was the switch assembly FIRST. That appears to be the most common item that fails, then he assumed it was the motor in the transfer case. He was amazed that it was the module, and indeed, a replacement had to be shipped to him.

Memory serves that the switch assembly is about $80.00---give or take. That is, from most internet sites, the most likely culprit. The module in my truck was about $280.00. I don't even want to think how much the transfer case motor is.

The fact my dealer had to go through this, one part at a time, indicates to me that there is not enough info in the service code computer to nail it down exactly.

If you are having a lot of problems in isolating this, you might just try bypassing the whole thing. Try out POSI-LOK. Here is a quote: "4WD ON THE FLY! 4x4 Posi-Lok is a "POSI"tive engagement device that replaces failure prone factory vacuum or electric front axle engagement systems. 4x4 Posi-Lok is simple and easy to install, and allows you to manually engage your 4 wheel drive--while sitting still or on the fly--from inside the cab for true 100% engagement every time. Posi-Lok works with manual-lever or electric push-button type transfer case systems."

Click here to go to their website. This might help.

adamryan7 · February 15, 2003

I just bought a 2001 Z71 with 85k miles. My service 4x4 light just came on as well and will sometimes engage into it but makes a noise (sounds like from the front left, maybe the front differential?) I'm clueless about this kind of stuff but want to learn. Does this sound like what you have dealt with and do you have any suggestions or thoughts? Thanks, Adam

AZ-Z71 · February 15, 2003

OK, mine push button switch went on mine and also a friend of mine, both truck '99, can't remember the mileage, I think mine was around 60,000 and hers 70,000. The message center light also came on which stated "Service Four Wheel Drive". I noticed if I played with the button sometimes I could get it to go into 4 wheel drive and sometimes the service warning wasn't on. Replaced the switch in both truck and have not seen the service light in neither since. (almost a year now)

Price of the switch is like $35 from the dealer but we knew someone that worked for the dealer and got them for around $27 each. Takes a matter of 5 minutes to change out. The dealer knows this is a common problem and always starts here first.

MT 1500HD · February 17, 2003

bbviper,

Had the same thing happen on my 2003 1500HD, four wheel drive would not work and the pilot lights next to the switches were all off.Tried turning the truck off and re-starting still same problem.I looked in the owners manual and found the fuse for that system (inside the under hood fuse box), I removed the fuse and heard a relay cycle, I re-installed the fuse and everything has worked fine since.Hope this provides a temporary solution.

MT

cyrylyn · February 17, 2003

OK, mine push button switch went on mine and also a friend of mine, both truck '99, can't remember the mileage, I think mine was around 60,000 and hers 70,000. The message center light also came on which stated "Service Four Wheel Drive". I noticed if I played with the button sometimes I could get it to go into 4 wheel drive and sometimes the service warning wasn't on. Replaced the switch in both truck and have not seen the service light in neither since. (almost a year now)

Price of the switch is like $35 from the dealer but we knew someone that worked for the dealer and got them for around $27 each. Takes a matter of 5 minutes to change out. The dealer knows this is a common problem and always starts here first.

this sounds like what happened to me - I'd get the "Service 4WD" message, mostly at high speed in 2WD, and my pilot lights would never illuminate unless I put a great deal of pressure on the switch housing (in between the buttons). The buttons still worked a little, but it took some patience. The dealer replaced the switch, under warranty (free), and I haven't had any problems since. Lights up, switches immeadiately, etc.

Farmer2 · November 1, 2011

I had just had the same problem on my 2000 1500 silverado with 245k on it.

I went straight to the dash switch panel and resoldered all the terminals where they meet the circuit board. That was it and saved me $40 for a switch. The switch comes out easily after removing the cowling, that snaps on. The there is a few tabs holding the back cover on to get to the circuit board to resolder.

I found that the switch was bad when I had the switch removed from the dash but still wires connected to it. When moving the wires on the back the pilot light would go off and on. I knew I was close at this point.

Hope this helps some others out as well ;-)

Dave

Farmer2 · November 1, 2011

I had just had the same problem on my 2000 1500 silverado with 245k on it.

I went straight to the dash switch panel and resoldered all the terminals where they meet the circuit board. That was it and saved me $40 for a switch. The switch comes out easily after removing the cowling, that snaps on. Then there is a few tabs holding the back cover on to get to the circuit board to resolder.

I found that the switch was bad when I had the switch removed from the dash but still wires connected to it. When moving the wires on the back the pilot light would go off and on. I knew I was close at this point.

Hope this helps some others out as well ;-)

Dave

MikeInCtown · November 1, 2011

FWIW check out car-part.com for items like the servo motors and control modules. The site is a conglomeration of all the boneyards out there and you can search by state, region, zip code etc... I bought a servo motor and control module for a GMC jimmy a few years back for something like $75 total. Sure beats the $300+ tag for the motor and $500 tag for the module the dealer wanted.