Last year while travelling to the NE part of the country, my "SERVICE 4WD" light started coming on sometimes, and only momentarily. The stealer replaced the cluster and, as an added bonus, my odometer would reset to "0" every time I turned the ignition off. They replaced it again and now I have the same indication as before. Anyone have an idea as to what may be wrong? We are getting ready to leave on a 3 month trip th the northcentral U.S.A. and I am a bit concerned about this problem.
Thanks
Richard

See http://dieselplace.com/forum/forum_posts.asp?TID=277&KW=service+4wd

jbplock
Thanks but my 4wd drive works as advertised. The only problem is a "once in a while" service 4wd light indication and it my come on every 4th or 5th time we start up.
Richard

Richard,


When my 03 was new I would occasionally get the "Service 4WD" message in the DIC but it would go away if I shut down and restarted. It finally got so it would stay on all the time and the lights on the 4WD button would flash.. It would even indicate it was in 4WLo when it wasn't. In my case it turned out to be the encoder/motor in the transfer case. The dealer said a bad switch assy will cause the same problem.. The encoder/motor problem was very common on the early 03's. Since yours is an 02 maybe it's the switch (??). Are you still under warranty? If so I would take it to the dealer and insist they fix it. Until it's fixed I would also remove the fuse for the 4WD. There have been reports of the transfer case getting stuck in 4WLO ... Not good when going down the road at 65MPH... The dealer who fixed mine said they had seen that happen. The owner continued to drive the truck in 4WLO on the highway and burned out his transfer case ... it was out of warranty too ... Hope this helps.. http://www.dieselplace.com/forum/smileys/Geek.gif Edited by: jbplock

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<H1>Service 4WD Indicator Illuminated, DTC B2725 Set (Replace Transfer Case Shift Control Switch) #02-04-21-004 - (04/15/2002)</H1></TABLE>"Service 4WD" Indicator Illuminated, DTC B2725 Set (Replace Transfer Case Shift Control Switch)


1999-2002 Chevrolet and GMC C/K Pickup and Utility Models (Silverado, Sierra, Avalanche, Suburban, Tahoe, Yukon, Yukon XL)


with Four Wheel Drive and NVG 236/246 Transfer Case (RPO NP8)<A name=ss1-877978><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=877978&amp;pubid=271&amp;evc=sm#ss1-877978" target="_blank">
<H5>Condition</A></H5>


Some customers may comment on the Service 4WD indicator illuminating. Upon investigation, the technician may find DTC B2725 set.<A name=ss2-877978><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=877978&amp;pubid=271&amp;evc=sm#ss2-877978" target="_blank">
<H5>Cause</A></H5>


The condition may be due to a intermittent fault in the transfer case shift control switch.<A name=ss3-877978><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=877978&amp;pubid=271&amp;evc=sm#ss3-877978" target="_blank">
<H5>Correction</A></H5>



<H4>Important</H4>


The transfer case shift control module should not need replacement. DO NOT replace P/N 15749703 unless diagnosis points to the module as the malfunction.





Replace the transfer case shift control switch using published Service Information procedures.<A name=ss4-877978><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=877978&amp;pubid=271&amp;evc=sm#ss4-877978" target="_blank">
<H5>Parts Information</A></H5>
<TABLE width="100%" border=1>
<T>
<TR>
<TH vAlign=bottom align=middle>


Part Number</TH>
<TH vAlign=bottom align=middle>


Description</TH></TR>
<TR>
<TD vAlign=center align=middle>


15709327</TD>
<TD vAlign=center align=middle>


Transfer Case Shift Control Switch</TD></TR></T></TABLE>

Thanks for the replies. I just checked for DTC's with my Hypertech and none were set. Seems like problem is becoming more frequent. What does this light tell anyway? Does it really need serviced? Has approx. 24k miles and is still under warranty. As I said previously, the cluster was replaced twice and this seemed to help for awhile. I am thinking GMWorld... and the TSB is very close but, no DTC's.
Richard

I had same problem, no codes set.


tech replaced module under truck near trans. No prob since.

hypertech won't pick up a B code....And 03's have a different set up than 02's.....

If under warranty ...take it to the dealership and have them check the DTC's in the ATC module most likely there is a B2725 dtc ....i have seen this problem alot ,the production switch has a short in it, the new switch had the problem corrected.

Thanks all. It's still under warranty. Will take it in on Wed and ask em to check codes. According to the first time, the code was P0650. They replaced the cluster.
Richard

I like the idea of my odometer resetting to 0 miles. I would have a new truck every time I drove ithttp://www.dieselplace.com/forum/smileys/Big Smile.gif

P0650 Is for a short for the MIL(check engine light) it has nothing to do with the service 4WD warning......maybe they are just padding their warranty........As a Flat rater would say,"It's NOT a RECHECK it's a REFLAG"

Scott,


During the winter, my "Service 4x4 soon" light would come on for about 10 sec at startup sometimes, and then go out. My truck never acted up in 4x4, though. Now that warmer weather is here, I haven't noticed it happening anymore. Would this be the same thing rvarner described?


Thanks, Tom http://www.dieselplace.com/forum/smileys/Pig.gif

Possible, the thing is after the short is detected , if the short is no longer present the code b2725 will clear itself after 40 key cycles.


The biggest indicater would be ...after the service 4WD light comes on, you cycle the key and the message goes away.......and this code will trigger no matter if you are using the 4WD or not.

Scott,


OK, I see. It would actually go away on its own after about 10 sec and not return during driving. When I had it in recently for its "last" warranty service, they couldn't find a code in the computer.


Thanks for the reply, Tom http://www.dieselplace.com/forum/smileys/Pig.gif

Tom,
Sounds like whats happening to my truck. Gonna take it in on Wed. so will let you know if they fix it. Even tho it's not serious?, it shouldn't be happening. Have also complained of, if truck sits for a week or so, transmission has a problem going into reverse. Dealer said they could not duplicate the problem.
Thanks, Richard

they delay in your transmission is most likely due to the torque converter bleeding down, the problem is with two springs in the pump, send me you VIN and i'll check to see if it applies to your truck....

hdmax,
Ooops, should have said "trip" OD. Yea, wish it would have been the regular OD too. No such luck.
Richard

GMWorld...
It's on the way via PM.
Thanks
Richard

GMWorld...
Took it in today and they had to order the switch for the SERVICE 4WD problem but, they agreed it wasn't the "cluster". Thanks for your help. Will keep the TSB on the torque converter for when we get back in Sept.
Richard