Service 4w drive

The clicking you her is the switch sending the signal to the motor on the transfer case that you are locking in 4x4, I would just be sure I was at a complete stop and in park or nuetral when you lock it in, I know it says shift on the fly 4 wheel drive but it is easier on it mechanically if you are at a stop.

check receiver at transfer case connection get nasty clean contacts
also check to make sure transfer case is working as designed/also check for ground

Yes larry is very correct.Try going in reverse.

On these issue,there are few solved help links for troubleshooting the issue easily.-------

Click the link below:---
No 4x4 light on dash?

http://repairhelpcenter.blogspot.com/2011/12/no-4x4-light-on-dash.html

-----------
4X4 Truck makes roaring noise in the front end?

http://schematicsdiagram.blogspot.com/2012/01/4x4-truck-makes-roaring-noise-in-front.html

-------------
Car will not go into 4WD high or 4WD low?

http://schematicsdiagram.blogspot.com/2011/12/car-will-not-go-into-4wd-high-or-4wd.html

--------------
No 4x4 light on dash?

http://repairhelpcenter.blogspot.com/2011/12/no-4x4-light-on-dash.html

------------
4 wheel drive system will not disengage?

http://technoanswers.blogspot.com/2012/01/4-wheel-drive-system-will-not-disengage.html

----------
4WD light is flashing and beeping? NO 4WD high?

http://schematicsdiagram.blogspot.in/2012/02/4wd-light-is-flashing-and-beeping-no.html

----------
2002 Jeep Wrangler: 4WD Idiot Light is ON?

http://technoanswers.blogspot.in/2012/06/2002-jeep-wrangler-4wd-idiot-light-is.html

----------

Traction control switch will not engage on 4WD High or Low

http://whoisbyme.blogspot.com/2012/10/traction-control-switch-will-not-engage.html

-----------

4WD light flashing and 4WD will engage after few minutes

http://repairhelpcenter.blogspot.com/2012/10/4wd-light-flashing-and-4wd-will-engage.html

------------
2008 Toyota Tundra: 4x4 Wheel Drive Light is Flashing?

http://technoanswers.blogspot.in/2012/05/2008-toyota-tundra-4x4-wheel-drive.html

----------
4x4 front differential will not engage the axle on ford?

http://technoanswers.blogspot.in/2012/02/4x4-front-differential-will-not-engage.html

-------
4x4 will not engage on Ford F150? http://technoanswers.blogspot.in/2012/02/4x4-will-not-engage-on-ford-f150.html

-------------
Dodge Ram 4x4 light keeps flashing 4X4 LOW LIGHT IS FLASHING ON DASH

http://technoanswers.blogspot.in/2012/09/dodge-ram-4x4-light-keeps-flashing.html

----------
Ford 4x4 front wheels will not engage?

http://technoanswers.blogspot.in/2012/02/ford-4x4-front-wheels-will-not-engage.html

-------------

These details will help.

Thanks.

It is the shift motor for the 4wheel drive - only problem is that a shop has to program the new shift motor to the blazer or it will keep doing the same thing

The  actuator on the front diff or transfer case is stuck or bad. This will send a signal back and turn on the service light. In 2003 I believe the actuator is on the front differential.  

if i am not mistaking these have the vacuum module on the front differential check it it is probably bad common problem on these trucks from 96 and up if it is the electronic type it could be one of three things the switch on the dash, motor on transfer case, or the electronic module for the 4 wheel drive.

Problythe moter on the side of the transfer case, if it is not the actuator on the frount axel. Moter on the transfer case is about 500 for my 96 GMC sierra. It is a dealer part only. The metal box under the dash will hardly ever go out but every one all ways wants to replace it.

For 4W Hi either be stopped or moving at a slow rate of speed (<20 MPH) and move your 4WD selector to the 4 Wheel Hi position.

For 4W Lo stop and move the selector from 2W Hi to 4W Hi then push down on the selector and move through N into 4W Lo.

you might have just had a bad connection
could you pleas rate my solution thanks
later paul

     There is a module behind the glove box that is known for failing. usually though it done work at all.