2007 Tahoe
Service 4 wheel drive warning light comes on but I can switch off by pushing button on dash ( ).
No trouble codes.
Will go into and out of auto 4w drive and 4wd high, but when put to 4w drive low, light just blinks.
Where should I start looking. 4 w drive has only been used sparingly.

Thanks
Kevin

 

Welcome to the Forum.

First of all, I'd do what it says. Get a Fluid Change on your Transfer Case.
Then, though it doesn't indicate it, have your Codes reset.
Then, use the "coasting procedure" to make the 4WD-lo engage.

Here's how to do that...

Place Transmission in 4WD-Hi.
Accelerate Vehicle to just over 5 MPH.
Shift to Neutral Gear while moving.
As forward motion drops just below 5 MPH, Press 4WD-Lo button.
Transfer to Lo should take place within 10-15 seconds.
You may have to attempt this several times, before a change to 4WD-lo takes place.
Once it changes, don't stop there, and change from lo to hi and back several times, to get things shifting properly.

This procedure can be use for transfer in either direction (Lo-Hi/Hi-Lo).
You many hear a respectable "clunk" upon the disengage transfer. (that's normal Chevy ;D).
Do away with the "sparingly" for engaging your 4WD-lo. and establish a regular brief use (like once a month) operation.
Drive it about a mile or so in 4WD-lo, and keep your speed at 30mph or less.

When in 4WD-lo, use light throttle pressure when accelerating, or, get a Neck Brace.