OBD2 Code reader and Chev Suburban with "Service 4WD" display
 

Hello,
I'm new to GM products. Bought a 2004 Suburban to pull my boat. Today it says "Service 4WD" on the dash.
Looking at the forum, I'm unclear whether a cheap Bluetooth OBD2 reader with Android software will read a code for that. Or even if a more dedicated reader off of Amazon will do it.
Is there a cheap way to get codes for this, which I'm assuming is a GM specific code.

Also, I found this website to troubleshoot the issue, which I have yet to do. Wondering if there are better troubleshooting directions, or if this is pretty good.

Thanks.

I did start the truck and noticed that none of the yellow dots were lit in the 4WD/2WD area. I pressed on the side of the area (not on any buttons) and then the 2Hi light lit up.
I suppose I have the poor solder joint problem or need new buttons then, right?

I would say so. Do a parts search and see if that switch is being made in the aftermarket. My old '99 Yuk switch was being made in the aftermarket and that tells me it's a issue part.

I re-soldered the plug connections on the switch and will give that a try.

Soldering seemed to work at first, but I think there's a different problem going on that is affecting more than just the 4WD buttons. But I'm new to Suburbans and certainly could be wrong.

We just got back from vacation and drove the Suburban on a wash-board gravel road while pulling a boat. When driving over all those bumps, some crazy things happened. The Airbag light and service airbag warning came on and went off. The HVAC blower fan would cut out completely and come back on. The radio lost all reception. It comes on but when you scan, it doesn't find any stations. And though the truck was in 2WD the entire time, sometimes the indicator for 4WD Lo was lit. Sometimes none were lit. One time neutral was lit. But the truck remained in 2WD.

The entire 3 hour trip back home on the blacktop highway had no issues, other than the radio still didn't bring in any stations (though my Bluetooth/FM Radio adapter would work - which is odd that the radio could pick that up, but not any other radio stations).

I suspect this might be a grounding problem and have read that on the driver side footwell there is a ground point that sometimes needs to be cleaned up. I'll get to that when I get time hopefully later today. Or, any other ideas?

I should also mention, there is an after-market remote car starter and lock/unlock feature. I didn't install it and don't know how long it's been in there. It has a factory radio/CD/Cassette.

And after our trip everything is working perfect. I didn't fix anything. The only difference is we're driving on smooth(ish) roads/highways and not a washboard gravel road.
Frustrating.