4X4 selector switch

[Raber43]

I have a 2004 Trailblazer EXT, 4.2 L.
The other day we were in a icy road situation and went to use the 4X4. Here is what happened, I went to 4hi and the light just flashed, I tried 4lo same thing, no matter what mode I tried the same thing happened, then the "SERVICE 4WD" light came on... The 4X4 worked in the flashing condition, and the "SERVICE 4WD" light goes out once the engine is off for a while... Any suggestions?

[the roadie]

How many miles? Have you ever regularly exercised the 4X4 system to make sure it works before you need it in bad conditions? Any history of it working or not working before? If you're over 50K miles, have you changed any of the fluids?

The system will not go into or out of 4LO without it being in neutral and coasting less than 5 MPH. But A4WD and 4HI can be switched on the fly.

In other posts you haven't seen yet without using a search, it's explained about how to interpret the noises you should hear if you turn the ignition on with the engine off, in neutral, and cycle the 4WD switch. There is a high pitched whine from the front axle actuator, and a lower pitched motor on the side of the transfer case. Try that experiment, and report back the noises you hear when switching between each of the modes.

Then we can guess better and not just suggest putting yourself at the mercy of the dealer.

[02SOMWS6]

not sure if this will work for you but it did for me. My 2wd light was blinking , you could switch it to 4wd and it would do the same thing. So I go to start my TB and the lights blinking again so quickly while it's still blinking I put it in reveres waited a second to feel it engage then put it in drive. The light stopped blinking and stayed on . I can now switch it back and forth from 2wd to 4wd. The 4wd does work now and the light stays on. It will stay on till you shut the car off. It might do it again on the next start up.....it might not. But for now it works for me. Let me know if it works for you

[bstromback2002]

Originally Posted by 02SOMWS6

not sure if this will work for you but it did for me. My 2wd light was blinking , you could switch it to 4wd and it would do the same thing. So I go to start my TB and the lights blinking again so quickly while it's still blinking I put it in reveres waited a second to feel it engage then put it in drive. The light stopped blinking and stayed on . I can now switch it back and forth from 2wd to 4wd. The 4wd does work now and the light stays on. It will stay on till you shut the car off. It might do it again on the next start up.....it might not. But for now it works for me. Let me know if it works for you

I have the same problem but i have to put my transmission into neutral within 15 seconds of starting the vehicle. If i don't do this nothing will change or activate as far as the 4 wheel drive system is concered it will stay in 2 hi. I talked to a friend at a dealer and he said it's do to the transfer case control module not waking up (sleepy as he called it) If there is a certain code in the computer it may need to be replaced. Or they just flash it with a new update.

And i definantly agree with roadie on what he said.