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Well, mom hijacked my car this morning because the Service 4WD light came on in her Trailblazer and she's afraid to drive it. I'm thinking she should be okay as long as she isn't trying to use the 4WD, but I just wanted to see what others thought about the potential causes.Any theories on what it might be? It's about a year old I think, so I'm wondering if there's some kind of maintenance that it's wanting. The 4WD probably hasn't been used but a couple of times, and definitely not recently since it's summer. So I'm not sure what might have set the light off if 4WD wasn't even engaged.Any ideas or things to test? Should she be afraid to drive it or should it be okay as long as the 4WD isn't on?Thanks guys

Bad 4wd select switch on the dash. 8 times of of 10. The other 2 times is the control module. Don't be afraid to drive it, it's a notice light, not a warning light.

Is the bad switch putting it in 4WD mode without you selecting it? I'm guessing it's not a warning light until it flashes, correct?

The contacts go bad, and the module can't tell if 4WD or 2wd is selected, default mode is 2WD. Yellow lights are caution or notification, Red means Stop the vehicle before you do damage.

Okay, thanks... I'll let her know! And then I can have my Vibe back!

glad to be of service!!

And you most definitely were! I figured somebody around here would have some sort of idea of what could be wrong. I'm doubting it's anything to do with the mechanics of the system, since it hasn't been used recently and wasn't in use when the light came on, so it probably is that switch.

A little more info...this really makes me suspect it's the switch... When the notice light was on, the lights on the 4WD switch were not working and it would not go into any other mode besides 2WD. Now, the notice light is off and the lights on the switch are working, and it will go into anything except 4WD Low. The lights being off when the notice light was on, and working when it was off, make me think it's losing its connection or something, and maybe it's just vibrated itself back into place or something...

Get it checked out resonably soon though... a friend of mine had that idiot light on and ignored it for a few months - turns out the electronic control had locked the front hubs and drive - but just a little. Not fully engaged the system wore a lot of the front wheel drive parts down and needed to be R&Red.Not cheap. But this was on an 1997 Blazer with Electronic control 4wd, so lets hope they improved the system since then.

As was stated earlier in the thread, I don't think it's parts, I think it's the switch tnpartsguy spoke of, since the light on the switch was off when the notice light was on, and vice versa. So I don't think anybody's going to need to get into the oil pan or that anything is actually torn up. That switch is in the dash and it's probably the only thing that needs any repairs. The Trailblazer actually isn't doing anything abnormal anymore, and the notice light has gone away. She plans to call the dealership in the morning to ask if she should bring it in or wait and see if it happens again.

silverawd26 is correct. Even if you're just tooling around town - every month or so you should engadge 4wd for a few miles.Its much like the emergency brake on an automatic - if you don't use it, the parts become unusable and will stick when someone finally uses it.I would imagine the manual also describes a recomended interval and suggestions on how to maintain the system. I truely hope its just a switch and is easily fixed. We're just giving you a heads up to not take it as lightly as some would - it could lead to very expensive repairs if it isn't just the switch.

Quote, originally posted by silverawd26 »Should of taken it in right away. It was Saturday and they were closed.As for the rest of that post, I'm not disputing that it is good for it to be run in 4WD and I never was disputing that, I'm just saying that doesn't look like what caused this. And besides it's not my vehicle and I don't drive it so there's nothing I can do for it, it's my mom's vehicle, she's the one who drives it.

Quote, originally posted by Kari »It was Saturday and they were closed.As for the rest of that post, I'm not disputing that it is good for it to be run in 4WD and I never was disputing that, I'm just saying that doesn't look like what caused this. And besides it's not my vehicle and I don't drive it so there's nothing I can do for it, it's my mom's vehicle, she's the one who drives it.So there Tomarrow will be fine. Seriously guys, I see these everyday, it's the switch. Sometimes just playing with it will make the 'Service 4WD' go off. yes, the 4WD needs to be excersied a bit, but it's not Kari's truck to deal with, she can pass on the advice, but that's about it.

Quote, originally posted by tnpartsguy »So there Tomarrow will be fine. Seriously guys, I see these everyday, it's the switch. Sometimes just playing with it will make the 'Service 4WD' go off. yes, the 4WD needs to be excersied a bit, but it's not Kari's truck to deal with, she can pass on the advice, but that's about it. Yep, and I did pass it on, but that's about all I can do. Do you think that they would be able to do anything for it if it only threw the light once and isn't doing anything odd anymore? I know I have bad luck with the Vibe doing things it only does for me, like a child...LOL.

Thanks, partsguy. I'll agree that the 4WD crap needs a workout from time to time. I know little of the mechanics of how it all works, but that would at least make some sense.I think it's the switch too... The problems with the truck appear to me as if they are far too erratic to be anything mechanical. Signs point to electrical for me. Don't worry guys, the truck will be fixed under warranty! And I don't see Kari's folks having to rip the oil pan out to get the 4wd working again or whatever.

They (Chevy Dealers) know this is a problem, shouldn't be a problem, it should have stored a code in the PCM.

Quote, originally posted by silverawd26 »You would think GM would do a recall and have this changed out if it is a known problem.Oh well.... GM's not the only guilty party at such things... insert auto manufacturer's name here at one point in time has been guilty of just the same.

Quote, originally posted by silverawd26 »I made the comment that the 4WD components go through the oil pan, which can be very costly. That's eff'ed up... Who freakin' engineered that junk?

Hate to say it, but... It would appear to me that this thread has outlived its usefulness. The original condition that prompted the thread to be started has been discussed sufficiently and therefore you might as well say a conclusion has been reached.Let's slam the door shut on this before things get too far out there in la-la land, please...

Quote, originally posted by silverawd26 »I made the comment that the 4WD components go through the oil pan, which can be very costly. Well I doubt that the switch in question extends all the way down to the oil pan, since it's in the dash. So I'm thinking that the discussion about the oil pan here is probably a moot point...heh.Anyway, like James said, my question's been answered, hopefully she called about it today, I have the Vibe back, and all is well.

I had a comment but will refrain after reading CP's post...

Yep, we're through. Thread Closed