2006 trailblazer indicates 4 lo but is in 2 wheel drive

It could be a junk switch or it could be bad contacts inside the transfer case motor.. Does the transfer case switch to the selected gears? Everytime? If so, you might try another switch. If it does the same, I would say the motor contacts are bad. Replace the motor if you want the lights, But I personally wouldn't do it until the motor quit switching gears. They're not cheap.

Have you had codes checked ? While connected to a good scanner that will check transfer case switch to show if switch is working, and it could be the switch on the side of the transmission.

More than likely it is the switch alot of electric 4-wheel drive switches have been known to go bad from lack of use

First of all, the noise is not coming from the rear. The noise is only happening in 4WD mode, that involves the transfer case and front differential.
When was the last time the transfer case fluid change, it is recommended that it be changed every 50K miles. It is possible that you have transfer case issues. It is not recommended to operate the drive system in Auto mode constantly, this will wear out the internal clutches.
If the road surface does not warrant 4 wheel drive, keep the selector in 2WD.

I was researching the recalls for the 2002 tundra and havent found any recall pertaining to the 4whl drive. Sometimes when people have their 4wheel drive locked in and drive on pavement for any length of time, whether it be just a couple of feet or a couple of miles, over time it creates a binding of the gears in your transfer case. Once the bind is so great, the engaging and disengaging starts malfunctioning and leads to bigger problems overall. I could be wrong about this being the problem that you have but I think its something to look into. It wouldnt hurt to put your vehicle up off all fours and release the bind if any by running through the gears while in 2 and rour wheel drive while all four tires can move freely and release. See if that works for you. Check your gear oil front , center and rear and use much caution when attempting this suggestion. Also refer to your owners manual troubleshooting section for other possibilities. Merry Christmas. By the way, the electrical switch should be covered in the troubleshooting section also.

Did you put the transmission in neutral before switching out of 4 lo? Try that and if that doesnt work, try neutral then hit 4hi then 2 wheel

Diodes are part of the electrical system that allow for electricty to flow in only one direction. They are used to help protect the computer systems in your vehicle. How fast are you going when you shift into 4-wheel drive?

Hi my name is Juan and I do own a trailblazer with the same year 2002 and I read the problem you have let me try to help you Have you try to shift to 4hi with your transmission in neutral ? the transmission needs to be in neutral in order to shift the transfer case to 4hi and the vehicle needs to be completely stooped also is your service 4wd light on?? if the light is on your transfer case needs service and it can be as simple as the switch inside your car or a solenoid that has not been detected by the computer

Just to clarify, the "transmission" is not stuck in 4-Lo. It is the "transfer case" that is attached to the transmission that actually engages the 4-Hi and 4-Lo modes. To properly shift your vehicle into 4-Lo, you know that you have to shift the transmission into neutral and slow down to less than 5 mph. Once your vehicle slows down to this range, your can switch your transfer case into 4-Lo mode. Due to the inner workings of the transfer case, the actual shift into 4-Lo may take a few seconds to complete. This is normal and does not signify that there is an issue. All transfer cases that have 4-Lo mode will act this way regardless of the make or model. To make a long story short, to shift out of 4-Lo you must follow the same steps that you took to shift into 4-Lo, just in reverse order. Switch the transfer case to 4-Lo mode if it isn't already there. Slow down to less than 5 mph (your vehicle must be moving, though). Then, shift your car into 4-Hi or 2WD. Give your vehicle several seconds to complete the shift. The transfer case indicator light will flash until it is complete. When it does complete the shift into the new gear mode, you will most likely hear a "clunk" (the range sleeve inside the transfer case disengages from its mating spline) from under your car. Again, any transfer case with 4-Lo (regardless of make or model) will exhibit this same noise. This should help you get out of 4-Lo. It is good practice to shift your car into and out of 4-Lo at least a few times each year to keep all of the splines free of corrosion and build-up. Based on the age of your vehicle, your transfer case may also need a complete flush and some new transmission fluid. Hope this helps.

if it is a 4x4 the switches are on the dash board in frot of you, in order
2 HI , 4 HI ,4 LO