The Dreaded "Service 4wd" message...

[Martinjmpr]

We got a late spring snow here on the Front Range of Colorado. Got almost a foot of heavy wet slushy snow here at my house.

On Saturday the wife wanted to look at furniture so we took the Suburban (2004 1500 LT, 4x4, about 156,000 miles on it.) Since it was intermittently snowy and slushy I put the truck into "auto 4wd." Drove all day like that until the end of the day when we were coming home through a mountain canyon with snow building up on the road, I went ahead and put it in "4 Hi" for about 2 miles so I would have sure traction. As soon as I got to the main highway it went back into Auto 4wd.

Sunday morning driving to get gas I switched it from Auto 4wd to 2 hi (all the snow was gone and the roads were dry by that time) and shortly after that I got the "service 4wd" message. I cleared it with the steering wheel button and it did not come back on. After filling up with gas, sitting in the parking lot, I decided to run the transfer case through all modes except N (I sometimes forget that there's a neutral on these!) It went into Auto 4wd, then 4hi, then 4 lo (with a noticeable "clunk" shifting to low) and then back to 2 hi. No problems, no warning messages and no indications that something wasn't right.

Is this something I need to worry about? Is there something I should be checking? I didn't really test out the 4wd, just made sure the dashboard buttons worked, and they worked fine.

Thanks in advance! I may be doing some mild 4 wheeling this coming weekend so I want to make sure the 4wd system is operating correctly.

 

[rockola1971]

The typical culprit is the encoder ring down on the shift motor. This ring gives feedback to the Transfer Case Module to let it know that it completed a commanded shift and is physically in that gear or atleast the shift motor is anyway.

 

[Fless]

^^x2

My '04 Hoe experienced the same sort of issue a while back. Dash switch would show 'neutral' when driving down the road, and other modes when I know it hadn't changed. Put a new encoder motor in it (you can rebuild them, too) and that cured it.

FWIW, I hear that a transfer case going out can cause the encoder motor to be taken out, but that's just what I heard. I recently had my TC rebuilt since it wouldn't put power to the front wheels, so I'm not sure if it caused the encoder motor failure or not.

 

[Martinjmpr]

How difficult is the encoder motor replacement? I watched a YouTube video and it looked relatively simple, but I would be interested in hearing from someone who's actually done it.

 

[jarydM]

How difficult is the encoder motor replacement? I watched a YouTube video and it looked relatively simple, but I would be interested in hearing from someone who's actually done it.

Same issue, everything works, still getting error message. Haven't crawled under to replace/check the encoder ring because I haven't needed 4x4.

I've read its easier to replace the whole actuator, and I've also read that this is really a much harder job than it looks like. I have no idea, because I haven't even started it. Curious if anyone has

 

[rockola1971]

Its not hard at all. The encoder is inside the shift motor. You have to remove the shift motor from the transfer case. To do that you have to drop the front driveshaft.