Hey guys I'm sure this question has been asked before but any help would be great.I have a 99 Blazer that I put in 4wd yesterday to get through some nasty weather. When I went to switch back to 2 wd, the drivetrain will not change back over and stays on 4 wd. Anyone have any info on what the problem would be? Thanks.

 

I'm not a mechanic but did have some 4WD problems on my 2003 Blazer this past week myself when cold weather and snow hit Seattle. My problem was that after shifting back and forth between 4WD Hi and 2WD a few times, it stopped switching altogether (I could get to 4 Low when in neutral, but not 4 Hi - I could hear the switching sound and flickering lights on the console, but it would actually switch over to 4 Hi). Turns out my battery was dying due to cold weather and lack of use for only 1 1/2 days. I changed the battery and everything worked fine. I did find some sites suggesting other causes, but this happened to fix mine. Hope it helps.

 

seadit, it was most likely the lapse on power supply that remedied your problem. A battery disconnect will reset the TCCM which often will result in everything working fine, sometimes for quite a long time. Most of the time though, the 4wd system will work great right up until you really need it.

Most of these types of problems are caused by encoder errors. The TCCM can work through some errors, but keeps track. Once the consecutive errors gets to a certain value, it will stop attempting to shift modes.