Recently bought an '03 Yuk XL - Service 4WD

[Scottydoggs]

theres a few different scan types in the app. its gonna be a C code iirc. P codes are power train, c and U codes are the other two types of codes.

 

[George B]

this free app https://play.google.com/store/apps/....obd2.chevroletsys.chevroletsysscanfree&hl=en and a droid device and a obd2 bluetooth reader can read all your codes. they list using the elm327 bluetooth. that ones now junk due to china clones flooding the market. use the bafx brand. its like 20 bucks.

Was looking for this app for apple and can’t find one.

 

[Scottydoggs]

Was looking for this app for apple and can’t find one.

pretty sure its a droid only app. tablets work for this app as well as old phones you might have laying around.

 

[George B]

pretty sure its a droid only app. tablets work for this app as well as old phones you might have laying around.

Was looking for this app for apple and can’t find one.

i bet there is something similar available. Like this: https://apps.apple.com/us/app/car-scanner-elm-obd2/id1259933623

 

[Fless]

I took your advice and picked up the BAF Elm327 reader and downloaded the app. It doesn't seem to give any transfer case codes even with the Service 4WD message on. Any thoughts on how to get the device to pick up the code? Would you mind walking me through it?

Thanks for your help-

I don't think I've seen the 4WD PIDs in Torque Pro, either, but it's been a while since I had it running in the Hoe. Besides, I use the Tech 2 and it has it all.

If anyone has a source for custom PIDs for the NBS SUVs, I'd be interested in trying them out in Torque Pro.

 

[MassHoe04]

Typically its the encoder ring (AKA Commutator or Shift motor position indicator). They get a dead/worn/dirty spot on them and the 4WD module gets lost and does not know what position(mode) the Tcase is in. Next time you are running without the message showing, shift into 4wd then 2wd then Auto4wd (if you have it) and exercise the Tcase. This typically cleans the encoder up if its dirty.

I had the message to service 4WD on mine a few months back. I "exercised" the thing pushing buttons to kick from one mode to another. Went back and forth a few times. Message never came back and everything seems to be working OK.

I am guessing that the PO, a retiree going back and forth to FL, never put the thing in 4WD at all in 180k miles.

Use it or lose it, as they say...

 

[houstontaylor]

My '03 Tahoe was doing something like that and after replacing the transfer case control module under the dash it worked fine. I had already replaced the 4WD switch with no luck. The transfer case had already been replaced so I figured the shift motor was good.

 

[waveryd]

Had similar issues with my 2004 GMC Yukon XL 2500. Did not show any DTC's on my Snap-On Solus scanner. Started with the cheapest, most likely culprit, the encoder ring and was successful. Mine would actually shift itself into 4 Low at a fuel stop after driving for a while! Fairly easy job to install. Just watch a video and make sure the gears are lined up. No issues since with mine.

 

[Gearz]

I had a 03 Tahoe LT and like wavered I also had to replace the encoder speed sEnsor because when I got in the truck it said I was in 4LO but it wasn’t it was just confused. LOL

 

[03yukXL]

Still working on getting the code read. The ELM module and any associated apps will not give you the code. One new thing I noticed, one day I ran the truck and there were no lights at all on the selector switch. I was looking at the wiring diagram here In this thread and note that the switch receives the 8v reference from the TCCM. I suppose if the TCCM was getting no signal from the encoder ring it could interpret that by sending no signal for to the selector switch, but I am thinking it’s much more likely I’m dealing with a bad switch or a bad TCCM, more likely the TCCM. I also haven’t had any symptoms of the truck shifting into unselected modes of 4wd. Wonder what you guys think?