Thank you Kyle, 4×4 problem – FIXED

I have a 2002 Blazer 4×4 with Auto 4X4. I had last used the Auto 4×4  successfully was on December 26 when we experienced icy conditions returning from visiting relatives in Northern California. I tried the 4×4 a few weeks ago and found that it didn’t work, just flashing lights in all but 2×4, but the transfer case motor operated and seemed to change the gearing. I searched and found this forum and immediately started educating myself, as the Chilton’s Manual I have is only good for a paperweight. Today I have been looking over the 4×4 system on the truck, locating components and etc. as pointed out by Kyle’s responses to other member’s problems. I finally found the vacuum control valve which is neatly hidden behind the wiring harness and some other connectors. Lo and behold – a vacuum hose right at the valve! I cut the hose, reattached it and now I have a functioning 4×4 system So, this is a huge thank you to Kyle and this forum for telling me what to look for and where to look for it! – Ted

15 thoughts on “Thank you Kyle, 4×4 problem – FIXED”

  1. I have a 99 blazer. Got the cable and motor but 4 low will not engage properly. Some times it will go in flawlessly. Normally first start. Normaly it makes a clanging sound and kicks back into 2wd. Sometimes when it does go in it will get stuck. It will go from 2wd to 4 hi perfectly. Any help would be greatly appreciated.

  2. Remove the switch from the dash and resolder the circuit board. Over time, they get a cold solder joint and loose connection. Hope this helps.

  3. First i would like to thank all that had anytning to do with this posting blog i followed the steps and found that my encoder motor was corroded and when the 4×4 was engaged before i got the truck they destroyed the motor and case getting a use one and will see if it fixes this problem

    Kyle’s reply;

    Hi Luke;

    I’m glad my blog was able to point you in the right direction! Good luck, I hope the encoder motor solves your problem!


  4. I just bought a 99 chevy blazer with 4×4 and auto 4×4 push buttons when i try to engage the 4×4 nothing happens no lights or noises. checked the fuses everything seems fine going to check the module in the kick panel as per your other blogs but if there is anything else that would kinda give me a head start it would be appriciated. by the way this blog is awesome reading some of the other posts has given some insight to different solutions

  5. Hello Ted;

    That is great news! I’m glad that my blog was able to help you locate your problem… that’s the whole purpose I put the information here. I’m happy to see it works! :)

  6. I also have no 4×4 and this is the situation. it is a push button system, i click 4high, the module in the kick panel clicks like it should, the light goes into 4high like it should. I checked all fuses on the truck, they are all good. I then checked the next obvious thing…vaccuum actuator, it has vaccuum going to it and operates fine by pulling on the cable that goes to the front end. i then put the truck on the lift and noticed that my front driveshaft is spinning, but still no front wheel drive. now the same goes for 4low. the module clicks and the light goes on like it should. the truck drives in the lower gear like it should, the cable is pulled by the actuator like it should, the drive shaft spins, but no 4 wheel drive. what do i look for next?

  7. This was my situation. I had no 4wd after going into a ditch back in late 2007 or early 2008. That summer I took it to the dealer and they supposedly fixed the seal from the transmission to the transfer case because transmission fluid had been leaking into it. That cost me $1600, about $600 more than what I had actually been quoted (including the transmission flush). I had told them to just seal it up because they had quoted me almost $3000 to fix the 4wd (they wanted me to get a new encoder motor and module). After getting stuck a few times this winter, I felt that I would go back to the dealer and complain to them (because I realized that my 4 low wouldn’t work, whereas it was working before I had taken it in to get the 4 hi fixed. After looking at your blog, I felt inspired to at least see if I could manually switch my 98 Blazer into 4 hi until the end of winter, and avoid this visit. After exploring under the vehicle, I discovered that the spot on the transfer case where the vacuum hose attaches was attached incorrectly by the mechanics. After rotating it 120 degrees, and putting everything back together, my 4wd worked perfectly. Fixing this saved me over $1000. I would recommend that anyone who has had work on their transfer case which resulted in the 4wd not working at all to just check this vacuum plug to make sure that it is oriented correctly. The best thing is, if the mechanics had put in the encoder and the module, the problem still wouldn’t have been fixed.

    Kyle’s reply;

    Wow! Some of the stories I hear just blow me away. I’m glad that some of the information here was able to save you some money, Justin — that’s the whole reason I put it here! ;)

    Thanks for sharing!


  8. Well Kyle, You and your site have again come through.
    It seems to be an aged vacuum hose on the vacuum solenoid on the fire wall. Cost to repair 10 minutes with a xacto knife and a whole lot of crow.
    Just pulled the lines off and cut off about 5/8″ of the tubing and put it back on.
    FYI and the readers when I tried to locate a new solenoid at a jobbers 3 out of 3 had listings for every thing else in the system but the solenoid. Dealer wanted about $120.00 for this part. I am starting to wonder about a conspiracy.


    Kyle’s reply;

    Hi Ivan;

    Glad to hear that you were able to solve your problem quickly,easily and (most importantly) cheaply!

    Thanks for your comments.


  9. I had heard noise coming from the front drivers side of the blazer when in 4 wheel drive. It sounded alot like my front wheel drive car when the cv joint went. Well replaced it and of course the ball joints.
    This seemed to only fix some of the noise. Now when in 4wheel drive I get a noise like the front differential is slipping or not fully engaging. It seems to be a metal on metal noise as if the splines are not syncing ro meshing.(really hoping it is not the differential expensive and pain in butt work on). My lights on the push buttons seem to be working properly but I have on occasion seen them flash. When this happened I had assumed that I had hit them by accident. It is the noise that bother me as it really does not sound healthy for any of the compenents.
    Any suggestions as to the possible cause or solution.
    I have checked the vacuum solenoid on the firewall and the hoses were connected and not cracked.

    I have noticed that when going up hills and the vehical is under load the heating system will change from the heat/defrost to vent and blow cold. I have assumed that I have a vacuum leak somewhere. Any thoughts on if this could be affecting my vacuum actuator under my battery. I really dislike tracking down vacuum leaks it seems to be the car manufactures magic money making program. They never seem to publish the vacuum schematics making it a real by trial and error task.

    I will be checking out all of the suggestions offered on you site. Thanks to you and all that contribute as I now know at least where to start with the simple and cheap fixes.
    Any and all suggestions and insights will be appreciated.

    Hi Ivan;

    Unfortunately, I have no answer for you as I am not a mechanic. I’ve simply posted some of my personal experiences with my own Blazer.


  10. Kyle,

    Thanks I am kinda grasping at straws and trying to avoid a trip to the shop and the huge bill that generally follows.

    Thanks anyway maybe some of your readers have had a similar problem.

    PS.the pop star cop very interesting and would be hilarous if she did not carry a gun.

    Kyle’s reply;

    Hello again, Ivan;

    I hear you in regards to having to take your Blazer to the shop… and that’s why I post the information that I do, in hopes that it will save people that dreaded trip.

    If you do find your problem, please feel free to post it here as it may help others with the same issue.



  11. I have a 2001 S10 4WD. I hit the Auto4WD or the 4HI button. I hear the click, I can hear a noise as if the transfer case is trying to engage, but there is no 4WD. I checked the TCCM – no corrosion. I checked the vaccum on the fire wall – no problems. The part underneath the battery seems ok also….any ideas?

  12. Thanks for pointing me the right direction. My on-dash switches weren’t releasing or engaging the 4WD on the vehicle, and through all the suggestions, I was able to learn that the module wasn’t clicking. A quick check of connections on the large connector appeared okay, so I went up to the switch on the dash. Removed and disassembled the switch and resoldered the circuit board connector terminals. Works like a champ now, every time! Thanks for not making me go to the GM garage to pay for hours of troubleshooting and a new switch.

  13. Hi, Can you tell me where I can find the body relay block on a 2000 GMC Sonoma. Any help will be greatly appricated. My 4×4 doesn’t work. The switch on the dash gets power but none of the lights, light up. Thanks Beau

    Kyle’s reply;

    Hi Beau;

    Unfortunately, no. I’m not a mechanic, sorry.


  14. Ok so ive read alot of your posts on this topic but just cant find one that suits my problem. i have a 1998 zr2 standard and when im in 2wd and press the 4hi button it will engage quickly and off i go but when i want to go back to 2wd it wont let me, i just keep hearing a clickin noise. so i checked the vacume switch and the top turned on the switch itself so i decided to change it. then i checked the pod underneith the batt box, running i took the hose off and there was vacume but with a friend inside pushing the 2wd button i could see it trying to realease the cable but it would only come half way out before going back in. so for the time being i just unhooked that hose and running in 2wd. just dont know why its not exhausting the vacume when i press the 2wd button. if you guys have and ideas that would be much apprecitaed! thanks

    Kyle’s reply;

    I don’t know either… I’m not a mechanic.

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