2003 S10 BLAZER 4X4; 4WD won't engage

I have a 2003 S10 Blazer 4x4 with the in-dash pushbutton selector.
4wd is used very very little, and recently when I tried to engage it, the 4wd light would come on and immediately go out. tried engaging the low 4wd per the owner's manual and same same. I doubt seriously if its transmission problems. Is there a solenoid or 4wd shifter motor that I should look at?
thanks

maintenance51@aol.com

The TCCM (Transfer Case Control Module), located behind the passenger side kick panel, controls the encoder motor on the transfer case. The encoder motor shifts the transfer case. When the encoder motor moves the shifter, it operates a vacuum switch in the transfer case that applies vacuum to the actuator under the battery. The vacuum actuator pulls a cable that is attached to the front differential. The right front axle is engaged with the differential and 4WD is obtained.

Check all fuses, listen for relays clicking etc in the TCCM, listen for encoder motor operation, check for vacuum at the actuator, check if the actuator cable is working. A common problem is corrosion build up between the encoder and the transfer case. There are several threads here in the forum on 4WD operation that may help also.

In addition to that, if the vehicle has the auto 4wd feature, there will be a vaccum switch with a vaccum line in and out, plus an electrical connection located in the direct center of the firewall at the highest point. The vehicle will not go into 4wd if the switch is stuck. Its a dealer item that costs 50-60 bucks. Before buying take the switch off and connect it to something with a good bit more amperage like a battery charger and give it a few taps with a hammer to free it up.

I have a 1998 Chevy Suburban and mine wouldn't go into 4wd either. Except in my case the 4wd light would just blink forever. I could hear the transfer case clicking so I assumed it was working. I could shift into low range and the transfer case would make the change, but the light would blink and I would have no front axle power. I took a gamble and just purchased the front actuator for $135 at the local auto parts store and it fixed my problem. I doubt this will help you with your problem, but maybe someone else out there has the same problem I experienced.

Welcome to the club, I had the same problem. Turned out I needed a new TCCM (a much cheaper fix than the dealer's suggestion to replace the encoder motor for $1200).