99 Blazer is stuck in 4 high. There are no SES codes, etc. pertaining to the 4 wheel drive system. I temp removed the drive shaft so I'm not running around in 4 wheel. When you press the 2 hi button all you hear in the TCCM clicking. So for $50 I bought a known working used one, it does the same thing. So what I need to know, what happens when I press that button, what happens after the button is pressed, is the TCCM first in line to the 4 wheel drive system or is there something else? Is it possible the 3 button switch is bad? When I press 2 hi or 4 low, the light indicator comes in, it blinks several times times while you hear the clicking sound at the TCCM and then it stops, still in 4 hi.

Is the TCCM doing its job but something after the TCCM is not working correctly?

I hear from others there is a fuse on the firewall, where exactly is it and what does it look like?

Is there a sensor, solenoid, or something else I'm missing?

Any ideas?

 

My 98 3 button system is doing the same thing. I can get mine back into 2wd by turning the engine off, turning the key to run and then pressing the 2wd button. It goes right into 2wd this way.

I haven't had time to check anything yet.

Might be the diaphragm under the battery tray not releasing the cable to the encoder motor. A $14-$15 solenoid down by the encoder motor is another well known culprit for going bad.

Then there's the possibility your encoder motor is bad.

Also, your three button switch can be bad.

I never get a code. I scanned it even with no dash light on and still no codes.

Hope it's one of the cheaper things.

Good luck...

ps. Try taking your hot cable off your battery and ground it or wait 30 minutes. This worked once for me.

 

Suggest taking the 4wd button assembly out of the dash, carefully disassemble it and re-flow all the solder joints. Be sure to use a soldering iron...not a soldering gun. The gun delivers too much heat for a circuit board.

May or may not fix this problem but has on others....and its cheap / easy thing to try.

 

I'm going to try this lanny,I haven't forgot about this idea. I do have a 25 watt iron for circuit boards.

Been busy with my K2500 plow truck. I didn't remember to run it much over the past 7 months and when we got 10" of snow here in Pa last week I was reminded the hard way that I really need to keep the truck lubed. Lost some break lines too. Then when I got that all fixed, the pump motor for my Myers e47 went bad.

Still though, Chevy rules. It's a tough 3/4 ton with s 350.

 

I did have a similar issue with my 2000 Jimmy, after taking it down a frozen level B road. I crawled underneath to discover that two wires coming out of the front diff hed been cut. After I put them back together with some butt spices and heat shrink, then zip tied them up above the skidplate, it shifted just fine.

 

I tried the battery disconnect today, no difference.

 

I am assuming that the transfer case is stuck in 4wd and not the front diff:
Take the encoder motor off and using a wrench, rotate the "bolt" to the neutral position. This will take the transfer case out.

Then with the encoder motor loose you can see if it is moving when commanded and if not, go from there.

Now if the front diff is remaing locked...then need to determine if the cable between the front diff and the vacuum actuator under the battery is stuck. Try pulling on the cable and see if it moves. Probably removing the actuator and cable will unlock the front diff...but not always.

Good luck.

 

I don't even think I'm getting that close, I hear a clicking sound in the dash and from the TCCM or I'm just hearing the TCCM and it sounds like its coming from the dash.

If the input shaft seal is leaking, that wont keep it from coming out of 4 wheel will it? There is plenty of fluid.

 

The switch was replaced today. Friend of mine pretty much took the front end apart to double check everything and it all looks good all the way back to the transfer case/encoder motor.

So for the time being we found a way to get in and out of 4 wheel. We installed shutoff valve to give/release vacuum. Works like a charm. We added it at the Tee Connector.

So our thoughts are the encoder motor is bad, is that a good assumption?

 

The encoder motor switches the transfer case. And I think with the 3 button style, the transfer case switches vacuum to the actuator under the battery to lock the front diff. Additionally, the vacuum switches only after the transfer case has switched to 4HI from 2HI; no change in vacuum between 4HI and 4LO.

So if the transfer case is switching okay, and the new vacuum switch installed unlocks the front diff, then I am thinking it is the vacuum switch on the transfer case that is stuck/failed....which is a bit of a "bear" to get to, but possible. I assume that there is no fluid in the vacuum lines coming out of the transfer case; is this correct?