Service 4WD

[RobertWYoung]

Well after coming home to Texas from skiing in New Mexico over the holiday, my Service 4WD message is coming on and it's not showing what mode it's in.

I've had this message before when switching from 4LO to 2HI after towing the boat up a steep wet ramp, don't think I was rolling like I should have been.

But that went away after restarting the truck.

It’s not going away this time.

Any clues on what this could be?

 

[My01yuk]

I have this problem and have been told that it is my 4WD selector switch. Replace it and it should be okay. replacing mine next month, I never use my 4WD so i'm in no rush to replace it. Cost between $75-$99 depending on where you get it.

 

[TheFuzz]

Could be the switch, or there could be a problem with your T-case. I'd get it looked at by a shop...but then again I have a pretty good warranty lol.

 

[nytahoe]

my fuse used to come lose in my 03 tahoe.

 

[RobertWYoung]

Well I found a Technical Service Bulletin (Text attatched) about the TCCM losing communications. So I pulled the fuse waited a minute and put it back in.

Controls come back on and the Service 4WD is gone.

It did start back up in 4LO but switched back to 2HI just fine.

If it happens again I have to take it in and get a new TCCM I guess.

 

[Dismay]

Just had my Service 4WD light come on last night, it turned out to be a blown fuse in the block under the hood, "ATC" (20 amp), hopefully this doesn't start happening regularly.

 

[rich5368]

I fixed this this past winter. If it's not the selector switch it's the TCASE encoder motor. It's lke $200. That's what it was on mine and haven't had a problem since

 

[Dismay]

Yeah the 94 blazer I owned previously had issued with the encoder motor a couple times...

 

[Dylan]

Well after coming home to Texas from skiing in New Mexico over the holiday, my Service 4WD message is coming on and it's not showing what mode it's in.

I've had this message before when switching from 4LO to 2HI after towing the boat up a steep wet ramp, don't think I was rolling like I should have been.

If it's saying service 4WD and not telling you what it's in it's the switch thats bad.

As for switching from 4LO to 2HI you can't be rolling when you do this. If your truck allows you to switch to/from 4LO at anytime there is a problem in your 4WD system. 4LO is only supposed to be accessed by shifting to natural with the truck running with the brake applied.

 

[RobertWYoung]

Don't have to be on the brake ...

To shift to the 4LO position, the ignition must be in RUN
and the vehicle must be stopped or moving less than
3 mph (4.8 km/h) with the transmission in NEUTRAL (N).
The preferred method for shifting into 4LO is to have
your vehicle moving 1 to 2 mph (1.6 to 3.2 km/h).
Press and release the 4LO button. You must wait for
the 4LO indicator light to stop flashing and remain
illuminated before shifting your transmission in gear.

---------- Post added at 03:41 PM ---------- Previous post was at 03:40 PM ----------

Or To shift from 4LO to 4HI, AUTO 4WD or 2HI,
your vehicle must be stopped or moving less than
3 mph (4.8 km/h) with the transmission in NEUTRAL (N)
and the ignition in RUN. The preferred method for
shifting out of 4LO is to have your vehicle moving
1 to 2 mph (1.6 to 3.2 km/h). Press and release the 4HI,
AUTO 4WD or 2HI button. You must wait for the 4HI,
AUTO 4WD or 2HI indicator light to stop flashing
and remain illuminated before shifting your transmission
into gear.

---------- Post added at 03:44 PM ---------- Previous post was at 03:41 PM ----------

It did it again when I came home from Colorado. I had it in Auto 4WD and the lights all went out. Only seems to do it when it's cold and wet. I took the switches out and re-soldered the pins but that didn't seem to help. I went through a drive thru car wash and it started working again.

I'm thinking it is a harness / connector issue on the T-Case itself. I'm going to go put it up on ramps and check it out.