I have a Chevy Trailblazer 2003 103,000 miles, service 4 wheel light came on , drove for 15 miles. When I turned it on again, light was gone , it did this before for brief periods, then turned off by itself. I haven't used the 4 wheel since winter. I did all maintenance incl. transfer case fluid, automatic transmission fluid. Should I have it checked ? The light is off now. Any poss. problems?. is there any other maintenance I should do for the 4-wheel?

First you need to have EBCM - electronic brake control module check for DTC'S - diagnostic trouble code's . If the light is on there is a code stored . I think most part stores can do this and for free . After you find out what code is stored , looking up that code in service repair information for diagnostic trouble shooting chart would be next step . There are a few codes too.
DTC C0035 or C0040
DTC C0045 or C0050
DTC C0110
DTC C0131
DTC C0161
DTC C0186
DTC C0196
DTC C0201
DTC C0240
DTC C0241 or P0856
DTC C0244 or P1689
DTC C0245
DTC C0283
DTC C0287
DTC C0290 or C0292
DTC C0455
DTC C0550
DTC C0558

Find the code do the diagnostic's , fix the problem , wiring issue's , a sensor , bad module ,what ever it is . The light will go out then . Here is a sample of code discription .
• DTC C0035 Left Front Wheel Speed Sensor Circuit
• DTC C0040 Right Front Wheel Speed Sensor Circuit

Seems to me that you have a hub bearing and/or cv axle gone bad. Did the ABS light come on?

o2 sensor

Yes the wheel sensor or sensors may be at fault here.

How old is your car? When did you have it serviced last?

sounds more like the spider gears in the front end !!!!!!!!

IT COULD BE A FUSE THERE ARE FUSES UNDER THE HOOD FOR 4 WHEEL DRIVE ALSO IF THAT DOED NOT WORK CHECK 4 WHEEL DRIVE SELINOID

check the lubricant in the transaxle, if it is low it will cause the light to come on.

if it's not going onto the ground, and it's not being burned, check the positive crankcase ventilation and the exhaust gas recirculation valves for oil seepage...also check your air filter, if its got oil on it replace the pcv valve.

i have 2003 trailblazer ltz 153 000 mileage i have code po440 .i changed gas cap and turned off the chech engine light... i made 300 miles and it was good and today morning i drove a mile and light turned on ..... what do i have to fix ...thanks