Service 4WD Message

richscorvettes · July 23, 2003

On a recent trip to the Super Chevy show in Indy we noticed the electronic transmission dash control lights changing from 2H to 4H and even 4L. Then we saw the "Service 4WD" message in the display.

I stopped at a dealer in Indianapolis and they found a service bulletin (#03-04-21-001C) of 6/24/03 on this problem. The fix is to replace the encoder motor sensor, reprogram the TCCM and inspect the front drive axle engagement sleeve for damage. Our local dealer has ordered the parts, some of which, are on backorder.

I searched for any threads on this subject but didn't find one. Maybe I used the wrong search criteria. Has anyone else run into this problem? If so, did the repair do the trick? Thanks.

Rich Lagasse

N900WM · July 23, 2003

Rich,

My truck has had the same message pop up three times. It only seems to happen when on a long trip, and traveling on the interstates.

The first time it happened, I was in a snow storm in Cleveland and the truck would not engage 4wd. I took the truck in when I got home and they said there was a reprogram that was required.

It happened again last month and I was told by the dealer that I had to bring the truck in when the message displays as they couldn't find any problems.

Of course the message only appears when I'm nowhere near the dealer! And then goes out when I shut the truck off.

The third time it happened was right at start up one morning. It would not engage 4wd then either. I drove to the dealer and the light went out before I got there. Once again, no codes, dealer said come back if it happens again. It's getting annoying.

I leave this weekend for an 800 mile trip and I'll be towing so we'll see what happens. I hope nothing!

And interestingly enough, my wife and I test drove a new Tahoe last weekend and the same message appeared when I first put the truck in reverse.

richscorvettes · July 23, 2003

Thanks for the quick response.

Our first notice of this problem happened about 400 miles from home on the trip to Indy. After going to the first dealer to check it out he cleared the code along with giving us the service bulletin. He didn't have the parts in stock to fix it. He said there wasn't anything to worry about in the meantime (?) until we could get it fixed. It's still a little disconcerting to be that far away and to see that message. The fact that the bulletin indicates to check for front axle engagement sleeve damage suggests that some mechanical damage could happen. It did still go into 4 wheel drive though when we needed it to get through the soggy showfield at IRP. Then it stayed off until another 400 miles of interstate driving and we stopped at a dealer in Reading, Pa. who went through the same process. They didn't have the parts either and the "Service 4WD" message returned even with only in-town driving without the car trailer.

I don't know if interstate driving has anything to do with the problem (doesn't sound reasonable) but in the first 2,700 we had on the truck it never appeared even though 1,650 of those miles was to the Detroit Autorama and back.

I guess the good news is that it is a recognized problem and there is a fix if the parts can be obtained. I'm waiting on our local dealer to get all of them now as there are several parts needed including: the transfer case encoder, seals, screws, prop shaft clamp and the front drive axle engagement sleeve (if needed).

Good luck on your trip and thanks for the response.

Rich Lagasse

N900WM · August 6, 2003

Hey Rich,

Just back from the trip and I had 2200 miles of trouble free driving. No messages.

However, I did run into trouble on the first tank full of fuel.

I was two hours away from home and showing 1/8th of a tank when she ran out of gas. I checked the trip computer and it showed a range of 32 miles. NOT!

On-Star took care of us. We had a bad head wind and think that did it but watch your fuel when your towing!

HendyPhoto · August 6, 2003

Good to know!!! Thanks!

richscorvettes · August 6, 2003

N900WM,

That's always a comforting way to travel - "no new messages"

Our dealer now has all the parts for the service bulletin and will install them next week. We just returned from a short trip of 400 miles and didn't get the message or any crazy movement of the dash lights. In the previous trips it came on after 400 miles but that might just be coincidence and I'm still going to have the fix done to hopefully avoid any future problems.

Good to know about the trip computer range. I believe it calculates the range based on the recent average MPG so it could be off I guess. The size of the tank is one thing I wish they had changed to offer a larger tank as an option. We do get much better mileage than with our previous tow vehicle so the distance in-between stops is greater but it would still be nice to have more in reserve. We usually try to stop at around a quarter tank. I just don't want to mess with changing the stock tank and fittings. We averaged 13.5 MPG towing through the mountains with the cruise set on 65 so I'm happy with that. I've thought about carrying a 2 & 1/2 gal can of fuel somewhere but am concerned about the safety aspect.

We're taking off in a couple of weeks for Corvettes @ Carlisle so we're hoping the Service 4WD fix works. Thanks for the tip and enjoy the summer.

Rich Lagasse