The 4WD is not working?

You need to check to see if there is power to the actuator on the transfer case when that happens. If there is, the actuator may be going bad. If there is no power, then you need to check the relay and the switch to see where power is lost.

Here is the wiring diagrams for the system and the fuse location as well with the transfer case actuator.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Check out the diagrams (Below). Please let us know what you find. We are interested to see what it is.

Yes! a post that helped I looked at the wiring diagrams and saw the ATC fuse helps run the system when I replaced it bam! all fixed I love this site.

When I put me trailblazer in four wheel drive it does not work but it sounds like it wants to kick in what would be the problem

check to see if there is power to the 4wd actuator on the transfer case. If there is, check the actuator. If there is no power, you need to trace the power supply to identify where the power is lost.

The "Service 4WD " Light is on. Also the four wheel drive is not working. What would cause this?
Well Ok you need 200 characters for this question to get read. I wonder if I have 200 characters yet. Ok I will try again to type 200 characters.

It could be several things. Since the light is on, you need to have the computer scanned to identify trouble codes. Most parts stores will do it for free. Have that checked and let me know what you find.

Switch works, lights do what they are supposed to. There is no dashboard indicator stating "service 4WD". There is no noise when changing modes.
I have tried removing the #8 fuse for 30 seconds and re-inserting it - no change.

have it scanned for codes might be the switch or encoder motor but you have to scan it first.

Because I am not sure what the switch is supposed to do... when I change from 2WD to AWD, 4HI, 4LO, it always does the same thing: flashes for 30 seconds and then stops lighting. Is it possible that it is a vacuum issue?

i dnt' think so but it could be you can check front axle that is where the vacuum goes not to tcase. autoparts can scan for free

Will not engage 4hi or 4lo or awd.......2hi is the only one that works. The lights on the selector Switch blinks over the selection when I turn the selector switch on th dashboard and I can hear the motor but it will not engage the front axle in 4hi or 4lo. The light only stays lit in the 2hi mode. Also the cruise control stopped working. I changed the transfer case/encoder motor last month and still no engagement. I recently changed out the actuator and now the blazer will not drive at all......I can rev it up and get the RPMs but its almost as if the transmission has stopped working altogether. I have checked fuse #8 under the front hood fuse box and also checked fuse #48 under the rear passenger seat.....fuses checked out ok. Would the transmission stop working upon replacing a 4wd front actuator? Thank you in advance for any assistance you may be able to offer.....

are you sure the fork is on correctly. it will do this non engagement if it is not properly installed.

Roy

I have a 2003 trailblazer which will not go into any of the 4 wheel drive options (AWD, 4WHI, 4WHL)
It seems to be an electricle problem. The lights flashes momentarily (above the selection) and then the service light comes on. Could this be the actuator?

Scan the computer for C-codes

Check and test the ATC fuse no.8 25amp in underhood fuse block if okay-Have the transfer case shift control module and the transfer case encoder motor checked out-

my cars service 4WD light comes on and the 4WD doesn't work, then i park it in the garage over night and it works the next morning i checked the codes and no codes are present. What could be the problem?

Either the transfer case control switch, shift motor, or transfer case control module.

If you are unfamiliar with these systems, have a dealer or trusted garage repair it.

4 wheel drive is not working the dial does not light and it doesn't engage what could be wrong?

Check the actuator on the transfer case to see if it is getting power. If it is, remove it and check it for operation. If no power, check the wiring harness for damage and the plugs for corrosion.

My 4WD wont come on

check all your fuses with a test light.

I just read somthing online that said take fuse 8 out and keep it out for 30 min. I will post if it works or not. also if you do this you have to look at the diagram under the first pannel you take off.

It did work if this happens to anyone take out fuse 8

I have a 02 trail blazer that I went out to go start today and the four wheel drive light is not coming on (non of the four wheel drive lights come on) I checked the fuse but still nothing, and it will not engage. What could this be and does any budy know how much this may run me?

You need to start by checking to see if there is power to the 4wd actuator on the transfer case. Do that and let me know what you find.

when I turn the four wheel drive to any position other then two wheel the light above that position flashes and then goes out and the four wheel drive does not engage. last year I put in a new switch a new module and something new at the transmission.

scan for codes and see if encoder motor is working on transmission or getting power. encoder motor is high failure rate. make sure to check relay and fuse under hood as well.

When i turn dial to 4wd or awd, the light comes on, but won't engage...when I rev it up it feels like it catchs every now and then, but wont engage...like it wants to but something wont let it...any ideas???

I would have to suggest that you have it diagnosed by shop because there are so many things involved in that system.these vehicles have a lot of failures of the transfer case encoder motor and the transfer case control module,but it could also be a shifter fork or the transfer case itself.there are so many possibilities.

When the temp out side is cold. say around 25 degree's when I start the engine the service 4x4 light comes on and the car will not engage into 4 wheel drive. After the weather warms up it works fine. Or after driving enough miles to get the car really warm then parking and turning off the engine, letting the car sit then restarting it seems to work fine. Is there a sensor or relay that needs replaced ?

I have the same problem with my 2004 trailblazer. And my mileage is about the same. It doesn't want to go into 4x4 when I turn the switch. Did you ever find out what the cause of the problem was with yours? Thanks

The 4WD was not working on my 2000 Chevy Trailblazer. I found the mechanism that puts the car into four wheel drive and followed the vaccum hose connected to it. The hose was broken near the back of the engine. I thought that I would be able to splice the hose to fix the four wheel drive, but the broken part of the hose is located in a place I cannot reach much less splice the hose together. So I my question is, is there a way to replace the hose completley or is there some other way I could fix this hose?

If anyone wants to know, I fixed this. I was eventually able to maneuver the hose to a spot where I could splice it and the 4wd works fine

This is the knowledge I have with my 1999 Trailblazer 4 door. I will switch while in neutral. When the button is pushed the light while begin to blink until switched into drive, if not put into drive it will either continue to blink or go back to the last mode used. Also there's two vacuum hoses under the hood beneath the windshield that I've had to fix before. There's the info that I for sure know. Hope it helps!!

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