4WD Not Working? Chevy Trailblazer Four-Wheel-Drive Problems

Updated on October 18, 2019

It's Winter, and the 4x4 Isn't Working!

Chevy Trailblazer 4WD Not Working?

It all started with a 4WD drive switch. Like many car repairs, it all snowballed from there. My husband was driving our 2005 Chevy Trailblazer, and when he went to change the switch into four-wheel drive, the switch wouldn’t budge. Instead, it broke off–through no fault of my husband I’m told–and the 4×4 service light popped on. Thus began our massive hunt for What’s wrong-with-the-Chevy-4WD 2013 (not to be confused with the-Chevy’s-brakes-are-still-squeaking-after-we-changed-pads-and-rotors 2012 fiasco). Is your Blazer’s 4WD not working? Keep reading.

The Switcheroo

Since the 4WD switch (which worked fine last year) seemed to be broken, and it was also relatively cheap to replace, that was our first move. $17 later, we found the switch wasn’t the problem. I thought that was way too easy. Even though it could turn without breaking off--a step-up from the previous one--the switch would simply blink when turned from 2WD to 4WD. When it stopped blinking 30 seconds later, the light would stay lit up on 2WD even though the switch was turned to 4WD. It was as if the rig was trying to go into 4WD mode, but couldn't make it work.

Upon further research with the help of Trailvoy.com (who knew there's a site dedicated to us), we found a guy who successfully reset his transfer case control module by pulling fuse #8 for 30 seconds, then placing it back in. But, he didn’t have the 4×4 service light on the dashboard. We tried it just for giggles: no dice.

After even further research, we found that many folks were finding success in getting their previously broken 4 wheel drive to work. We nodded our heads in agreement and excitement to find countless stories of others who shared our exact same issue. However, they were finding many different solutions: 4WD switch, fuse replacements, wire grounding problems, actuators/ encoders, Dorman vs AC Delco. This is where is where it becomes confusing! Also at this point, based on what others were forking over, we were saddened to realize that we might actually have to shell out substantial money to fix this problem.

4WD Still Not Working…

Being the adventurous DIYers we are, we found a Dorman actuator on eBay that would fit and patted ourselves on the back for only having to pay around $100 to fix this potentially pricey problem. NOPE. After that didn’t work (thank goodness for “returns accepted” policies on eBay, although we did pay for shipping here and back), we called Aamco. I told the guy my problem and symptoms, and he immediately guessed it would be an actuator problem. He invited us to bring it in and let them take a look…for $180. Just. To. Look. Needless to say, we went back to FREE researching on internet forums.

Upon even further research, we found that the words “actuator” and “encoder” were used interchangeably on many websites, and wondered if maybe we were buying an actuator when we should’ve been buying an encoder. We once again patted our savvy selves on the back and bought a $150 Dorman encoder motor on Rock Auto. NOPE! Not only did it not work, but the rig didn’t even recognize it at all–none of the switch’s lights would light up. Maybe there were other reasons for this happening, but at this point, we didn’t care any more. I was ready to give up and simply not drive the wintery roads, lest this be me:

Oh Shoot, Oh Shoot, Oh Shoot...

Almost There...

Luckily, I had one final trick up my sleeve--dear old Dad. He and his mechanic buddy took a look. He said he had seen aftermarket encoder motors fail to work, and that an original AC Delco actuator might still do the trick. Come to think of it, I did see that written in a forum somewhere at some point, but it was the most expensive option, of course (with the exception of a visit to the "stealership").

The Thrilling Conclusion to our 4WD Problem

ACDelco GM Original Equipment Transfer Case Four Wheel Drive Actuator with Encoder Motor #ad

We bought our final part, this ACDelco GM Original Equipment Transfer Case Four Wheel Drive Actuator with Encoder Motor for around $200 on Amazon. As an Amazon associate, I earn from qualifying purchases. I found a short video (below) on Youtube about how to install it. We collectively held our breath after we popped it in and turned the switch. I'll never forget the satisfying clunk of the motor shifting as it should. Sure enough, the ACDelco acuator with encoder motor did the trick. No more service light, no more non-moving switch mode light, and no more images of this mama sliding all over the road. We can hear the rig shifting when we turn the switch...and what a glorious sound it is!

Now, if we can only figure out why the driver's side headlight keeps burning out every few months...

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.


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    • profile image


      8 days ago

      I have a 2007 trailblazer. I took my truck to a shop because its riding rough. The mechanic fixed my bald joint. But he told me that my fwd is out. Thats why it sound rough when you drive. Is that true.

    • profile image


      4 months ago

      Thank you for your article of your 4wd repair adventure. We are having a similar issue with our Trailblazer. I enjoyed your humor throughout your article.

    • Boisegal profile imageAUTHOR


      5 months ago from Boise, ID

      Nice. Keep us updated.

    • profile image


      5 months ago

      Having same problem also . I work at a salvage yard so I can change parts as necessary. Think I will start with encoder motor thank to your post.

    • profile image


      9 months ago

      I bought a used transfer case for 474.80. I must have been ripped off. Since yours was only 200.00. Plus warranty. My wife noticed it. Envoys are about the same. It was not the changing switch. My Chevy.

    • Boisegal profile imageAUTHOR


      16 months ago from Boise, ID

      Could be front differential, but I don't have experience with that problem. Check out gm-trucks.com.

    • profile image


      16 months ago

      How can I fix grinding noise in the awd. Sounds like bearings grinding.

    • profile image


      16 months ago

      Got a 2004 trail baller and I switched to awd while moving and it never went into gear and now it grind’s all the time. Please help me.

    • Boisegal profile imageAUTHOR


      18 months ago from Boise, ID

      I like the idea of starting with a cheap, common solution and working my way up to the more expensive fixes if needed.

    • profile image

      Katie A 

      18 months ago

      I enjoyed your story, I am hopeful that it will work w the fuse answer as my 4wd lo was working just fine couple of days ago and now wont stop flashing when I try to engage it, the rest of it works but not the lo

    • Boisegal profile imageAUTHOR


      19 months ago from Boise, ID

      You could try the Delco actuator with encoder motor pictured/linked above. Sounds like you may have the same problem we had (and are now currently coming across in our 2008 Chevy Silverado)! Pay attention to a seller's return policy: sometimes you can send a part back part if it doesn't fix your problem, though there might be a restocking fee. Good luck!

    • profile image


      19 months ago

      Need input i got a 2006 trailblazer 4wd.and when i put it in 4 wheel drive the light flashes on the switch but no 4wd.high or low it worked last year not used it since. Any suggestions

    • profile image

      Gary Dannenberg 

      21 months ago

      Hey Scotty, love your stuff. 05 trailblazer. Took out ALL BOLTS and hoses to remove radiator. It seems like its stuck to my condenser coil. Some rubber clips or fittings seem like they are catching on each other.


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