REVISED.03 Trailblazer 4x4 won't engage

What Shep said. More info needed, are the lights on the dash switch off? Or are they on, but when you attempt the shift, does it just blink continuously and then revert back to the position it started from?

If there are no lights on, you need to remove the "atc" fuse which is located in the fuse box under the hood. Remove it for at least one minute with ignition off, then re-install and see if the the system "wakes up".

If you have a solid light on in the 2hi position, and then it just blinks when you attempt the shift to 4hi or auto4hi and returns to the 2hi position, this is telling you that it's attempting the shift but not all the parameters are being met. In that case, it could be any number of things. It would need to be scanned for codes and have the data stream checked to see what's actually going on. There are also numerous software updates for that particular vehicle/t/case in those years. Often the reflash will fix many problems.

Ian

the lights are off and no blinking, took the atc fuse out and still nothing

In that case, you better take it to a professional.

Ian

I am having the same problem with no lights at all on the switch position. I have an 2002 TB LTZ. I have removed the "4WD" fuse from under the rear seat and it looks fine. Any other ideas on what it could be, besides the switch not functioning? The switch position lights do not come on when the car is started either. It seems to me like if there were a major problem with the transfer case I would be getting a "service 4wd" dash indicator. The 4WD worked well a few weeks ago, but is only 2wd now. Thanks. Kenny

Try removing the "atc" fuse in the fuse box under the hood. Leave it out for 1 minute and then see what happens. If your 4x4 lights come back on, you need a software reflash. Actually, in 2002, often the atc module has to be replaced and then reflashed with the latest software.

Ian