I've had an on going fault with the 4X4 system on my 1999 Blazer, it has the automatic transfer case NV246. The lights were not working and 4 lo not engaing. I replaced the switch, which to my disappoinment didn't cure it, but then did after driving over a pot hole. So I removed the TCCM and found the connectors both rather dirty and corroded. I cleaned them up but the motor/power switch connector (4 pins) is still in poor condition, however, now 4 lo engages and 2 hi. I think the vacuum actuator is faulty so the front axel is still not engaging so that needs to be sorted when I get to it.
So, does anyone know if the connectors, both cable and and pcb are availible, I've looked on ebay without any success.
And, I've never seen the "service 4WD" light, ever, maybe someone cut the connection, so does anyone have a NV246 wiring diagram.
There are lots of posts about 4WD issues on here, I wonder how many may be down too the same sort of issues with electrical connections ?

 

Following on from the previous message, I have now got all modes working, including Auto 4wd !
After checking the vacuum actuator, I found it was fine and held vacuum but the hose to the vacuum solenoid was sheared off ! re-connected and now all modes working !
I'll replace all the vacuum hose at some point and will report back with some pictures.
So in summary of fixing my 4X4 fault;
New dash switch required.
Cleanup of tccm module connectors (Ideally new connector required)
Repair vacuum line to actuator.

One question though, how does the tccm know when the front diff is engaged ? So it stops flashing the light ?