HI I AM HAVING AN ISSUE WITH A 98 BLAZER, 4X4 3 BUTTON DASH SWITCH, IN PARK OR DRIVING WHEN YOU PUSH 4H NOTHING HAPPENS(NO LIGHTS).IF YOU STOP AND PUT IT IN NEUTRAL AND YOU PUSH 4H THE 4H AND 4L BUTTONS FLASH A FEW TIMES THEN IT GOES BACK TO 2H.IF YOU PUSH 4L IT DOES ENGAGE IN 4L BUT THE 4H AND 4L LIGHTS BOTH STAY LIT.I CANNOT GET IT TO GO IN 4H.I DID SOME TROUBLESHOOTING BY CROSSING OVER THE DLC PIN 13, AND THE LIGHTS ON THE SWITCH WOULD ALL THRE FLASH 2 TIMES, SO IM ASSUMING THAT MEANS TCCM CODE 2? WHICH I THINK IS ENCODER MOTOR.I DID SEE SOME SOME INFO ON HERE ABOUT TESTING THE SWITCH COULD BE FOUND IN THE TECH ARTICLE SECTION BUT IM HAVING TROUBLE FINDING THAT SECTION ON THIS SITE,IM SURE ITS RIGHT IN FRONT OF ME BUT I CANT LOCATE IT?.ALSO COULD IT BE THE ENCODER MOTOR IF IT IS STILL ENGAGING IN 4L JUST NOT 4H?, I HAVE RULED OUT VAC LINES SINCE IT DOES LOCK IN 4L?i KNOW I DO HEAR A WEIRD NOISE ALMOST AS A VAC ACTUATOR BEHIND THE RADIO EVERYTIME I PUSH THE BUTTONS BUT I DIDNT THINK THERE WAS ANYTHING TO DO WITH THE SYSTEM THERE?ALSO IF IT HELPS IT HAS BEEN WORKING ALL WINTER IT JUST RECENTLY STARTED ACTING UP,DIDNT MEAN TO CONFUSE ANYONE WITH ALL THE QUESTIONS BUT ANY HELP WOULD BE APPRECIATED,THE 4X4 HAS DEF BEEN NEEDED THIS YEAR IN INDIANA. THANKS

 

i had the exact same issue on mine turned out to need new TCCM on passenger side kick panel and the motor when the encoder motor is bad it will just shift from lo or 2wd cause it cant read in-between anymore just one extreme to another but it sounds like your module might be bad too this is what mine was doing before the TCCM and motor was replaced solved all the issues

maybe this will help trouble shoot if you need more ideas
http://john-stichnoth.com/MiscFiles/...leshooting.pdf

 

Well...you don't have to yell. Here's the tech article I think you might be looking for. https://blazerforum.com/forum/tech-a...ill-help-7180/

 

I took my 1994 Chevrolet S10 Blazer Tahoe LT to the Local Chevy Service Department today. It was the Transmission Case Encoder Motor. $142.99 at Advance with a $20 core charge. GM has the part but it is $500 and will take a few days to get there. It cost total to track down the problem and put the new motor on $258.00 So if you are having this problem and it is not your switch, vacuum lines or TCCM then it is the Transfer Case Encoder Motor. Hope this helps someone else that has this problem