I have a 99 Silverado. When going from 2wd to Auto, 4hi or 4low, the 4wd will engage and work, but the 4hi, 4low or Auto 4wd button will continue to flash. Could this be the switch on the dashboard? Has anyone else ever had this issue? Thanks!

thats a new one, normally when they blink either the solenoid in the diff or tcase is not working

Yes, it'* very odd. Today the button stopped flashing and went solid after a few minutes of being in 4wd. From that point, it started working normally. No 4wd service light either. I'm just glad the 4wd works.

Has their been a drastic change in temperature outside since you experienced the first issue?

Yes, I would say so. I purchased the truck in December, 2013. Since then, it'* gotten a lot colder (in Wisconsin) and we've a had a lot of snow. The truck stays in my garage when I'm not at work though. Today, I went ice-fishing and put it in 4wd once on the lake. It went into 4wd right away but the button continued flashing for a few minutes, then went solid (staying in 4wd). Once off the ice, I switched it from 4wd to 2wd, then to auto 4wd. I worked flawlessly then. I did take the switch panel out today, unplugged it and plugged it back in to see if that would make a difference.

The flashing then going solid is an indication that when something is engaging, its slow. Like Justin said, its either the front diff or transfer case solenoid. If your setup is like our S10'* and Blazers, I'm going to lean towards the typical faulty vacuum modulator or just a cold front diff.

When was the last time the front diff oil was checked?

I just checked it and added about 8oz to it yesterday. Drove to work today and tested the functionality. It worked like a charm.

Outstanding, that'* good to hear.

Yeah, I hope it'* not short lived. Now to clear these two engine codes...P0171 and P0174.

no vacuum crap on the full size ones fortunately, they are electronic solenoids. which will work better when warmed up if they are getting older.