Blazer Service 4WD Light

Sometimes when I start my 99 Blazer the Service 4WD light comes on and then goes right off like the other dash warning lights. When it does this properly the 4 button switch seems to work properly and I can change from 2WD to Auto or 4WD as normal - the appropriate button is lit up.

But sometimes when I start the car the Service 4WD light goes on, blinks off, and comes back on and stays on. When it does this there are no lights on the 4 button switch and it does not switch from 2WD, Auto, 4WD, etc.

It seems to matter if I turn the ignition on and wait about 3 seconds before starting the car. When I do that, the thing work properly (most of the time). But it's when I just turn the key and start the car immediately that the Service 4WD light stays on and the switch malfunctions.

Any guidence? Much appreciated.

It sounds like a bad electrical connection. These units are known to get corrosion on the Transfer Case Control Module connector, The orange connector on the module for the 4 button 4WD trucks. Remove the passenger kick panel to get to the TCCM, remove the connector and look for corrosion on the pins.

I have a 2001 full size z71 chevy I put in the shop for that same problem and another problem. They had to replace the switch that changes it from 2 to 4wheel drive. He said it was a common problem they run in to with those switches. Don't know if thats the same problem your having but I hope this helps.
Fiserman