C0308 fixed but still "Service 4WD"

[johnnyCZ]

This damn dummy light issue harasses probably all NBS trucks with various causes.
All of sudden, I got the "Service 4WD" light on on the dash. I was able to pull the C0308 code using AutoCal scanner/programmer. By following the troubleshooting instructions, I was able to find the cause which was a bad pin on the shift motor connector:


I fixed that by inserting a small copper plate inside the connector which assured a good connectivity. The C0308 disappeared instantly.

BUT, the ******** SERVICE 4WD light is still on. Tried to reset the codes, pull BCM, ATC, and 4WD fuses (they're all good) but no dice. Is it normal to observe this? There's no code at the moment (via AutoCal). I have also checked the 4WD switch which has perfect resistance readings.

Any guess or hint appreciated

 

[Chubbs]

Just from what I've experienced recently with 'service 4wd' when driving through any kind of water, the backsplash floods the connectors and disables the system. Last time, I unplugged the main TC connector and found water inside. I left it unplugged overnight to dry and the next morning when I plugged the socket it was back in working order and the message display for 'Svc 4wd' was gone. I made sure to tuck the connectors up out the way best I could while I was at it. I also cleaned the grounding on DS frame rail since I've heard of that creating problems. That's all I have for you.

 

[johnnyCZ]

Thanks. I checked that ground location too and looks OK, I checked even some other locations. I didn't drive it in wet weather recently when the C0308 came up, but I had the tranny and t-case separated since I replaced rear main seal (at least there's not any oil leak at this stage, lol).
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I'm starting to consider that I will buy some GM Tech 2 off eBay. I've seen one available here in Europe for price ~300-400 USD. Not sure if it's original or Chinese knock-off but I'd hope that it would work at least and I could enter some BCM programming and stuff. It could help me to dig more into the electrical systems.