“Service 4WD” message

[LTG515]

2004 Tahoe Z71 w/ about 155,000 miles.

I did a little digging on this forum and found a couple threads on this issue, but still had some questions.

Today I got a “Service 4WD” message on my cluster display and also noticed the lights indicating 2wd, 4hi, and 4lo were not lit up. I use 4WD pretty often and haven’t felt or heard any issues. I think I got lucky because it seems like the transfer case is stuck in 2wd as compared to others I’ve read have had it get stuck in 4lo.

Anyways, from reading, it seems like the usual culprit is the encoder motor which seems like a simple fix, but I was also wondering if there are any other 4WD components (4wd actuator, transfer case control module, or 2wd/4hi/4lo switch) that should just be replaced as well? I know it could be a little more expensive, but I just wanted to know if there are other parts that ought to be replaced while the works being done. Since I do use 4WD often I’d like to nip this in the butt and not have to worry about another factor of the 4WD system act up.

Thanks in advance for your suggestions.


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[Doubeleive]

Sometimes it is the one on the transfer case, sometimes it is the one on the differential, sometimes it is the button switch on the dash, being the lights are out on the switch that would be my 1st suspect. just speaking from experience, without a tech2 or similar tool like a snap on etc it's really hard to say 100% which is the case without a little trial and error.
when my dash switch went goofy I could hold the button down say for 4hi while turning the key to run and it would switch and light up, then I could turn the key off, hold the button down for 2wd and turn the key to run and it would switch back to 2wd, but the light would either go out or light up 2 at once or go out completely after a few minutes or if I cycled the key.

 

[LTG515]

Sometimes it is the one on the transfer case, sometimes it is the one on the differential, sometimes it is the button switch on the dash, being the lights are out on the switch that would be my 1st suspect. just speaking from experience, without a tech2 or similar tool like a snap on etc it's really hard to say 100% which is the case without a little trial and error.
when my dash switch went goofy I could hold the button down say for 4hi while turning the key to run and it would switch and light up, then I could turn the key off, hold the button down for 2wd and turn the key to run and it would switch back to 2wd, but the light would either go out or light up 2 at once or go out completely after a few minutes or if I cycled the key.

Yea I don’t have one of those cool scanner tools. Ok so maybe start with the dash switches huh because the lights are out? I looked that up and is a real cheap fix so wouldn’t hurt to start there. Only like $25.


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[Doubeleive]

Yea I don’t have one of those cool scanner tools. Ok so maybe start with the dash switches huh because the lights are out? I looked that up and is a real cheap fix so wouldn’t hurt to start there. Only like $25.


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ya I would try to find a oem one I think they run about $90, the aftermarket ones get a bad rap with people saying they fail quite often. I would see if maybe a transmission shop would be willing to run a scan on it before dropping any money, I'm just sharing what is most common to happen, sucks when you buy a part and it doesn't solve the problem, if you do that try and be careful to not leave any marks or anything on it so you can return it if it turns out to not be the issue. some stores wont allow returns on electronic items.

 

[LTG515]

ya I would try to find a oem one I think they run about $90, the aftermarket ones get a bad rap with people saying they fail quite often. I would see if maybe a transmission shop would be willing to run a scan on it before dropping any money, I'm just sharing what is most common to happen, sucks when you buy a part and it doesn't solve the problem, if you do that try and be careful to not leave any marks or anything on it so you can return it if it turns out to not be the issue. some stores wont allow returns on electronic items.

Ahh ok good to know! Yea probably smart to get it in for a real diagnostic. Thanks a bunch for your input [emoji1303]


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[Fless]

When you turn the key to the on position, do all of the 4wd mode switch lights cycle through the different modes? They should. The switches can be an issue, but you can pull yours and ohm it out, clean the contacts, and reflow the solder joints if you're relatively handy. If you don't find the thread that applies to the switch test with an ohm meter, post up again and we'll find it for you.

Here are some threads that might be of interest to you. Check and clean the grounds on the underside of the body, under the driver's seat, too.

https://www.tahoeyukonforum.com/threads/another-service-4wd.112896/

https://www.tahoeyukonforum.com/threads/service-4wd-and-no-4wd.110018/

EDIT: in what part of the country are you? Someone nearby with a Tech 2 might be able to take a deeper look into it. That's what solved my issue, which ended up being the encoder motor. YMMV

 

[LTG515]

Ok, update:

After the Service 4WD message coming on and the transfer case buttons not lighting up, I drove home and didn’t end up driving the rest of the day. The following day, yesterday, there was no service 4WD message, the transfer case lights lit up and stayed on 2WD, and I was able to cycle through 2, 4hi, and 4lo fine.

Today I brought it to a buddy’s shop who has a blue point microscan 3, plugged it in, but no codes. Unsure if it’s because everything seems to be working now and there are no stored codes, or if this scanner is just unable to retrieve that kind of information.

So not really sure where to go from here other than just see if it happens again...?


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[George B]

Ok, update:

After the Service 4WD message coming on and the transfer case buttons not lighting up, I drove home and didn’t end up driving the rest of the day. The following day, yesterday, there was no service 4WD message, the transfer case lights lit up and stayed on 2WD, and I was able to cycle through 2, 4hi, and 4lo fine.

Today I brought it to a buddy’s shop who has a blue point microscan 3, plugged it in, but no codes. Unsure if it’s because everything seems to be working now and there are no stored codes, or if this scanner is just unable to retrieve that kind of information.

So not really sure where to go from here other than just see if it happens again...?


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You could wait for it to happen again but there should be a code stored. I would put $$ on it being the switch in the dash.

 

[LTG515]

You could wait for it to happen again but there should be a code stored. I would put $$ on it being the switch in the dash.

I thought there would be one too. Maybe it was just the scanner I was using couldn’t access that info. The switch is kind of what I’m thinking also at this point.


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[George B]

I thought there would be one too. Maybe it was just the scanner I was using couldn’t access that info. The switch is kind of what I’m thinking also at this point.


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An easy thing to try if you can solder. Pull the dash switch and separate the case. Check and re-flow the solder for the four or five large terminal tabs. if you look closely several might be cracked. I had photos of this and found a thread on it a year ago but I cant seem to find it again.