Ok how many of these damn Blazers experiance this problem at some point. From all the threads I see of this a whole bunch. Here is my situation, I have a 2001, when I try to engage the 4wd high button all tht happens is all the lights will flash I hear the tccm clicking and it goes right back to 2wd, it never engages the 4wd. The dealer replaced the tccm last year, also a corroded wire end at the transfer case, the 4wd worked perfect last winter, now it has this problem. So far I have tried a new tccm, no change, pulled the batt. out and checked the accuator valve, good, also checked the vacuum hose that goes to it from the firewall, good no cracks. Im stumped, need help, thanks guys.

 

Will it go into 4Lo?

 

Have you checked all of the connections?

I'm assuming that you have the 4-button switch in the dash since you mentioned the vacuum line to the firewall. If this is so, have you measured the resistance from each button on the switch? A quick search for "NV236+resistance" with an author of "swartlkk" will turn up the required values you should be seeing.

 

Quick update on my 4 whl. drive problem, Its FIXED, it was the 4 button switch on the dash. WHOO HOO. Dealer part 45.00 and Im in business, just before the snow starts to fall, EXCELLANT.