Hey all, first post as a member! (So I apologize if I'm exhausting an old topic)

Less than a month ago, I had the 4x4 system (push button) on my 1994 Blazer fixed. The transfer case, transfer case seal, and the Hi-Lo switch were all replaced. The computer system was also reset to eliminate any error codes.

I used the 4x4 on two occasions since then and it worked flawlessly, however, the other day, I was driving into town (during a winter blizzard) and I decided to put it in 4-Hi. When I pressed the button, BOTH the 4 Hi and 4 Lo lights flashed 5-6 times and then stayed illuminated. Despite this, the 4x4 wouldn't engage. I pressed it again, and both lights flashed again 5-6 times and shut off. I then pressed it again, and got nothing...

I have read up on several other postings relating to the 4x4 switch not working(including the one error_401 posted about general 4x4 troubleshooting, which I found very informative), yet I couldn't find anything that had the same symptoms as mine.

Since it was 5 below zero that day, I'm not sure if the weather had anything to do with it, or if I was doing something wrong that made it like this.

Any help would be greatly appreciated!

 

When you select a mode shift, (2HI to 4HI, or 4HI to 2HI) the TCCM checks to make sure it's OK to actually perform the shift, (wheel speed, vehicle speed, wheel slipage, transmission gear, ABS, etc etc). If everything is ok, the TCCM will command the encoder motor to perform the mode shift. If the encoder does not report back to the TCCM with the correct data, or the front axle engagement switch does not change state, the TCCM will command the encoder to revert back to the original mode. Can you hear the transfer case try to shift? (usually clunks or clanks a bit)

 

No, I don't hear the sound. I also tried shifting it while in park and neutral. It just gives me those 5 flashes from the switch panel.

 

Might want to check the electrical connector on the TCCM for corrosion, fairly common. Could be a problem with the encoder or its wiring. There are a few threads on the forum that give some good advice, seems like one is titled "4WD no worky".