Before I knew any better, I purchased a used pushbutton 4x4, 2001 GMC Yukon.
I now frequently get a "SERVICE 4WD" message on the dash. What should I do
now? The thing clears up when the vehicle is restarted. The dealer doesn't
read a code and the problem will not repeat while it is in the shop. Should I
purchase a OBD scanner and leave it connected so I can see if the code shows
up while driving and I get the message? What is typically the failure mode of
these systems? When this occurrs, I cannot shift the 4x4 system. I'm afraid
I'll get locked up in 4x4Lo at some point.
Message posted via CarKB.com
Dont worry about it getting locked in any 4x4, because this sounds like your
computer (Transfer Case Control Module) is about to take a crap or the
Encoder Motor (the motor that shifts) is taking a crap. If its the computer
it should go back into 2hi by default. If its the Encoder motor I dont know
what to tell you. We had the same problem with our 99 Jimmy it has the 4
button sytem (auto4hi)
On Thu, 21 Sep 2006 01:24:45 GMT, "clwomble via CarKB.com"
Oh the wonders of push button 4x4 and the reason I would never own
one. It is normal for the service light to come on when code it set
and the light will reset when vehical is restarted but code should
still be readable from memory. Try scanning it while light is on.
In that year, the most common problem was the dash switch. There
are two types of "trouble codes". Current, and history. In your case,
there is almost always a history code 2725 if it's the dash switch. If you
don't have any codes in history, the other option might be that you need
to have the ATC (automatic transfer case) module reflashed with the
latest software. The dealership will have the ability to do this. The
maximum that they should charge you for reflashing the module (if in
fact there is an applicable update) is .6 hrs at whatever their labour
If you happen to get an 0327 code either current or history, you
may have an issue with the position sensor in the encoder motor.
This issue was not a big problem in the early years, but now we
see it on a regular basis. In this case, you remove the encoder
motor and replace "only" the position sensor.
Hope this helps.
I had the same exact problem plague me off and off for the first 6mos of
owning my new 2003 Silverado Z71 - it took about 6 trips over 6 months
for them to replace the pushbutton control module. They reset the
computer several times because they never found anything wrong - finally
I managed to get it in there when the error occurred - fortunately it
never came back once they replaced the switch. I found if you pull the
fuse to the 4WD module,leave it out a few seconds and then put it back
in and restart all would be fine - that told me it was electronic and
not mechanical. You are correct in assuming that whatever mode you are
in when the error occurs you are stuck in, but removing/reinstalling the
fuse would be a temporary fix that only takes a minute to do.
Good luck getting the issue resolved.
My 2000 had this problem three years ago. After reading this NG I knew the
problem with the switch was so widespread that others had even come up with
a way to fix the switch. I bought a new switch for $50 and installed it
myself, I haven't had a problem since.
Bottoms Up Divers
My 2000 is doing the same thing. When I first start it up, I get a
Service 4x4 message for abour 2-3 seocnds. It's intermittent of
course. I took it to the dealer with a laundry list of problems and
they said they'd fix it. I noticed the next time I used 4 hi, that the
issue started coming back again. I am not sure if they cleared the
codes or replaced the switch as the switch looked physically the same
so for $50 I am thinking I will just go ahead and replace it. Was
replacing this an easy job? Did you get the switch from a dealer or
I got the switch from a dealer but the parts guy was a dive buddy and I got
a it for what it would have been sold to a repair facility.
Installation was simply:
1) Remove dash trim around switch (no tools - it pulls off)
2) Remove a few screws holding the switch
3) Unplug the wire harness
4) Plug in new switch and reinstall
Bottoms Up Divers
A generic ODB II scanner probably won't pull the code as the transfer case
is not emmissions related. You would need the GM tool for scanning
non-emmissions codes. I bet it's an expensive tool because it is not
mandated by law to be compatible with other manufactures like the emmissions
items are - sort of like ODB I.
My 2000 4x4 Silverado 5.3 LT had the "Service 4x4 message".... in 2nd
Problem was cold solder joints on the 4x4 Push Button switch...
Replace the $50 Push Button Switch unit & the Prob should go away
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