I have a 2000 trailblazer with about 123K miles that had working 4 wheel but after this last huge snowstorm that hit the east coast it has stopped working. I push the 4 HI button and all it does is flash at me and it doesn't even sound like its trying to switch into 4 wheel. Im not a gear head Im a EMT so fixing people is what I know, so if anyone has any ideas for me I would really appreciate it.
have a good day yall

 

The four most common problems are the encoder motor (mounted on the tc), the tccm (transfer case control module), front axle vacuum actuator, and if you have the four button 4wd the vacuum actuator solenoid. I've had the pleasure of all but the motor failing on mine. My suggestion is take the kick plate on the passenger side off, that's where the tccm is. First take the tccm out and check the wire harness for corrosion easiset cleaned with baking soda and water if needed. Next with your driver door open turn your key to the on position not running, now hit the 4hi button and see what you hear. From the tccm when you turn the key on you'll hear some clicking (easiest heard with kick plate off) then when selecting 4hi it should click again sending signal to the encoder (and the vac. actuator sol. in the case of the four button). If all that works out next is the actuator sol. mounted on the fire wall just above your distributor (assuming you have 4 button). Start the truck and in 2lo put your finger on top of the solenoid there should be vacuum, now switch to 4lo it should be gone now that it's supposed to be re-directed to the shift actuator. If that works the vac. actuator is under the battery tray, if you pull the tray there's two bolts that hold the actuator to the inner fender. Remove them to free the actuator to check it for tears in the rubber and squeeze it to pull the cable to make sure it isn't siezed up. Hope this is helpful I don't consider any of this stuff hard at all cause minimal tools are required, mostly patients.

 

Yep, check all of the stuff listed above (along with many other threads on diagnosing the NV236 transfer case). If you need to get more indepth than that, you really need a high quality scan tool to access the TCCM and perform further tests.

 

thanks for all the advice!

actually now that i think about it i have a 3 button, 4 HI and LOW and All wheel drive. would it change any of the tips you gave me?

 

Well, actually, yeah. Like a lot of it...

Check out the Drivetrain section of the Tech Article Index link in my signature. There are a number of threads covering common problems and how to check your NP233 TCCM for codes using nothing but a paper clip.