my 2004 chevy blazer will not engage into 4 lo or hi when you push the button? How do I know its on or working?

What are the lights on the switch doing?

the lights just stay on. we can hear it shifting, but nothing happens, and still does not engage. we tried to pull he fuse out, didnt work, we tried to put it in N, then switch to 4, then park, still nothing. we tried going in reverse and drive a few times, still nothing.

Does the light change from 2wd to 4hi? Or will it blink then just go back?

There's a vacuum operated actuator under the battery tray. Hook up a hand vacuum pump and check that it operates and holds a vacuum. If it does follow the vacuum line back up to the solenoid that operates it on the firewall and inspect for any cracks that may cause a leak. Verify that the solenoid is receiving power when trying to engage the 4wd on the vehicle, and verify functionality of the solenoid by applying 12v to it. If everything checks out there, you are most likely looking at a failed transfer case motor as the problem.

take it to a transmission shop and have them look at it! most likely its your transfer case and will need rebuilt dnt cheap out and get 1 used 1 from a junk yard or anything youd be better off getting it rebuilt i own a 2000 4x4 and have been down this road trust me man

No, these problems are 90% of the time electrical or the vacuum actuator problem. If the transfer case is bad it will usually make some horrible noises.

mine's kinda doing the same thing it will goin into 4X4 some times but most the time the light's on the switch just blink and go back to 2hi or don't do anything but every once in a while it will lock in and the 4x4 works backwards untill bout 3000 rpm and it starts poping but will not work going forwards it only grids can anyone help

I fix my 03 blazer today it was just vacuum actuator cable sticking .sprayed it worked it buy hand and spraying it .Works great now was going in 4 low but not 4 high when I pushed 4 hi both flash and went back to 2 wheel

I don't have an answer. I want to know the same thing my 2003 won't go into 4 w hi. It did last week and couldn't get it out. Finally got it out. Now can't get back to 4 hi

mine goes into 4x4 gear but the front tires don't spin what is this??

It's most likely the transfer case encoder motor, which is either bad or its ground wires are corroded. It can also be a bad transfer case control module. Both are pretty cheap and very easy to replace.

I have an 04 Envoy and I just replace the transmission actuator because that's what the local dealer told me needed done. Once I replaced the actuator, I hooked it up, connected the battery and then I turned the knob to AWD and it worked!! Once I took the jacks down and tried it again, it failed! The 4 wheel drive would not engaging again. I moved the knob to AWD and it gave me the same message, "Service AWD". When I took it to the mechanic I told him that the module needed the software updated or reloaded. He came back and said that it wasn't the module but the actuator and it cost $650. Now that else can I look at? Any ideas?

I drive my 2004 trailblazer in 2wldrive is that right? Or should I be driving it in 4wheel?

Trying to diagnose my 4x4 issues. I can't seem to find the actuator solenoid that supposed to be on the firewire. I replaced the actuator and am tracing the hose to find the solenoid. I found a t value behind the engine near the firewall. One part is capped. Don't see any dangling electric lines to show me where the solenoid should be. Are there some model 2001 zr2 blazers that don't use the solenoid? My rpo code is np1. Any suggestions would be helpful. Thanks.

I replaced my 4 wheel drive computer for 2004 ZR2 on the passenger side bottom right under the side panel from someone on ebay. the serial numbers have to match or don't buy it . My blazer was stuck in 4 wheel drive low.. could not get into 4 wheel drive high after driving to the store. Switch light blinked and moved to each position but nothing.. heard clicking noises down on right front passenger side.. Worked again after replacing module.