Service 4WD light on 1999 Silverado

[Mosey]

I tested the 4WD while in the yard. When I was not moving and in neutral, I pushed the 4 High button, nothing happened and the light did not come on. I pushed the 4 Low button and I heard a sound below that I assume was the transfer case switching to 4 Low and the light came on. I pushed the Auto button and heard the same sounds (I assume from shifting back to high range) and that light came on. I pushed 4 High again and the light came on this time. I drove around some and I could tell it was in 4WD by the way it steered when I turned sharp. I switched in and out a few more times and everything seemed to work normally. So, maybe something was just sticking and freed up. The thing I'm not sure about is that the front wheel drive axles turn all the time, even when 4WD is not engaged. I'm referring to the shafts that have a boot on each end (which I assume is covering U-Joints) going to each front wheel. I know this because I had my wife drive real slow while in 2 High and I could see them turning. The front drive axles on my 1989 Suburban do not turn when it's in 2 High. It has a straight axle with automatic locking hubs.

[TBAILEY]

HAD THE EXACT PROBLEM WITH MY 99 ALSO DEALER
REPLACED THE 4WD SELECTOR SWITCH IT SHORTED
OUT. COST AROUND $150. [img]/forums/images/icons/smile.gif[/img]

[agcomike]

I had a 96 that would do that then it suddenly started down shifting into 4wd hi and then once going 80 it tried locking into 4wd lo if it had syncronized it'd locked up and probaly flipped or who knows what.

I'm a ase mechanic and determined that the wiring harness near the front axle where it hooks to the harness was getting wet and caused it..

[magsters]

I have a 1999 112K mi also with the same problem of the Service 4WD light intermittently coming on..I took it to the dealer and they said nothing is wrong with your 4WD..Is the dash difficult to get off to check the wiring?

[jwstewar]

Magster,

Chances are it is your switch. The dealer can't find it, because the terminals crack inside and sometimes they work, sometimes they don't - that is when you get the Service 4wd light. If you go back and read the entire thread, I've got some pictures on how I replaced my switch almost 3 years ago now - haven't seen the Service 4wd light since. Though we've only put about 20k on it since then. It sits in the garage a lot since we bought the Trailblazer.

[Zosostl]

Hello all. I seem to be having the same problem.. But My truck is a 2003 silverado 5.3 autotrac. It only has 48,000 miles.. maybe it is the switch too?? I sure hope not. when i bought it i opted not to get any kind of extended service warranty. but i'm thinking that with only less than 50K miles it shouldn't have a bad switch?
It only happened today for the first time. I disconnected the negative battery cable and it fixed it for now.. I will keep you posted as to what happens.. for now i'm going to do the forget about it technique and see what happens..

[contactbluebird]

I have just bought a 2000 silverado 4X4. Just a few days of owning it the SERVICE 4WD light came on. I was upset to say the least. I got on the net ( Google ) and searched "SERVICE 4WD" and this sight came up. I read all of the posts about the replacing of the switch in the dash. So I purchased a new switch and replace it and the light has not came back on as of yet (went on a 425 mile trip after the fix). Thanks for all the help! [img]/forums/images/icons/laugh.gif[/img]

[jgmont]

Just to follow up on the service 4wd light,I have a '99 Z-71 with 140,000 mi. and the auto trac system.Came across this site through my search engine,and saved me a considerable amount of money.The dealership down here in Alabama wanted $85 just to hook up the diagnostic machine and said the fix would be anywhere from $250-$450.After reading the threads in this forum I went out to the truck turned the ignition switch to the on position and noticed that all the lights on the selector switch did not come on like they should've during the first 2-3 seconds,which is a self test for the unit.Went and pick up a switch at the same dealership for $70.Installed the switch,turned on the ignition switch to the on position all lights came on,drove back home 4wd light hasn't came on.just another reason why I don't trust dealership service departments.probably would've took my money and wouldn't be none the wiser.Thanks!friends.

[brittanie22]

I was driving up my hill in the snow...and I Pressed the 4WD (4H) to drive in snow and it went in fine ...when I was leaving my house going down my hill I put it 2wd...and the SERVICE 4WD came on immediately after...then I tried to put it back in to 4wd and it doesn't work. so in the snow...im pretty much screwed. How much do you think something like this would cost? [img]/forums/images/icons/frown.gif[/img]

[jwstewar]

I think most of us were paying about $60 for the switch. Not sure what is going for now as mine has been replaced for several years now.