I purchased a 2002 4wd Blazer LS 3 days ago from a private owner. I swear when I test drove it and activated the 4hi with the push button the indicator light blinked several times and then remained lit. I tried it today and it blinks continuously and never stops blinking. I'm assuming that 4wd. is not engaging. I have the transfer case type described in the owners manual as "Automatic Transfer Case". I tried doing a search before posting but couldn't find anything. I hope someone can point me in the right direction to fix this so I won't have to go to the dealership. My Blazer only has 48000 mi. and shows no sign of severe use.

 

This symptom is usually the result of actions expected to take place during the transition of a transfer case mode change which has not happened. When the transfer case changes from 2WD to 4WD, for example, the front axle is Locked by the transfer case shift control module. If the transfer case shift control module does not sense that the front axle is applied, it waits for the action to take place before the gear change is made. While waiting, the mode switch lamp will continue to flash for a period of time, at which time all other mode requests will be ignored for the duration of th ignition cycle.

Are you driving when you push the button, at what speed and switching to 4Hi or 4Lo?

 

Yes I am driving. I first tried it at about 10mph. then at about 35mph and also stopped in gear .The results were the same. Just the light blinking in 4hi or auto. 4whl. until I push the 2hi button and then that indicator stays lit.

 

I just used the search function at the top of the page and see that there have been many threads on this issue.
Here's one, https://blazerforum.com/m_47982/mpage_1/tm.htm#50967 Hopefully this helps. Let us know if it helps or not.

 

I will try jumpering pin13 tomorrow and post results. Thank you for giving me a direction

 

I have also done a search and earlier posts indicated that "Auto 4wd will require a tech 2 or similar scan tool to read the TCCM codes". Mine is an "Automatic Transfer Case". Will I still be able to jumper pin13 to ground to get a code?

 

You might be right and I might be wrong https://blazerforum.com/m_56175/tm.htm
You might not have a pin in #13, which means you need it scanned.
Check your ATC fuse.

 

Hi I had the same problem with my 2001 jimmy and i unplugged the battery for 1 hour and every things fine now maybe it will help you ?

 

I had that problem once, turned out a vacuum line was off.

 

I disconnected the battery for an hour that didn't help. I don't have access to a code reader. I will look for a vacuum line problem. Any other thoughts? Thanks for all your responses.