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Service 4wd message

CHEQ6

Full Member
Joined
Apr 3, 2008
Messages
50
Location
Niceville, FL
I'm troubleshooting a Service 4WD message in the DIC when I first start the truck (2007 LTZ 6.0L). I have already cleaned the actuator connector, checked the frame ground and cleaned, and started to look for the transfer case module to check the connectors but can't find where it is located. I looked behind the passenger footwell kick panel but did not see it. I also plan on doing a drain and fill on the front diff and the auto transfer case. The owner's manual says 2qts of 80W90 for the front axle and something called Auto Trak II for the transfer case. Is there another name for Auto Trak II as I believe that's Chevy's name.

I have not changed any parts as I haven't had a code download done yet. I wanted to do the simple stuff first before taking it in to get a diagnostic.

Any and all inputs, suggestions, good fixes, etc. will be greatly appreciated. I've had this truck since 2008 and the only issue was a transmission fail at 68K miles. I have 148K on it now and got my first CEL. It's the oil pressure sensor per the code. I'm waiting for a few good weather days to change that as it's a PITA to get to. I figured I'd fix the 4x4 issue while it's down but I need to know what's wrong.
 
  Auto Trak II is GM's T-Case fluid. It was dealer only at first
you can find it in most auto parts now. Some later T-Cases
call for ATF and track II in the same year.
Some say you can switch to ATF. I asked the shop I purchased
my replacement T-Case if I could run ATF. They said mine called
for the Trak II use it.

 
Recently had a problem (07 at 185k) with my 4WD and ended up being the encoder motor at the transfer case.

Last Spring replaced the oil pressure sensor... and omg  :E: ... it's in an awful spot to get at. Ended up breaking the connector stem from the first one I tried installing. Not sure what differences there may be with the 6.0L vs my 5.3L as far as access to the pressure sensor. All I can say is, take your time, have the right socket for the pressure sensor and it may help to have two socket u-joints to get the angle right.

The transfer case on 07s is different than 08+ and calls for Auto Trak II while later models call for DEXRON VI fluid. I would just put Auto Trak II fluid in and only use genuine stuff. I am curious though as to whether DEXRON VI can be used in place of Auto Trak II.
 
Update: I cleaned the connectors and changed out the front diff fluid and the transfer case fluid (Autozone had the Auto Trak II). I can now get the switch to register all modes and I can get 4wd to engage. I no longer get the service 4wd message on start up but it does come up after 4wd is engaged. It does not disengage and does not make any noise but I still don't like the message popping up. The Accutron code scanner has provisions for checking transfer case codes but comes up as no link established. I'm pretty sure it's a sensor and it looks like I may need a trip to the dealer for a diagnostic. I can replace whatever the diagnostic calls out. Thanks for your help and any more suggestions/inputs are appreciated.
 
Go to the passenger side, front axle and pull on it where the cv attaches to the axle itself. There should be minimal movement if any at all. My thrust washer got worn through inside the axle and allowed the axle to disengage causing the service 4wd message for me but 4wd wouldn't stay engaged. Found that out in a massive snow storm.
 
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