So, ive spent hours looking through posts and could find only one with my exact problem, and noone ever replied to him. I dont consider this wasting my time becasue i learned a lot of things! Hopefully someone will be able to help me....

98 Blazer LS, 2dr, 4x4, 4.3L vortec, automatic, 3 button (np233)

The main problem: I have no 4Lo. (yes i tried in neutral/under 3mph) i get the blinking light in 4lo for ten or so seconds,then it and reverts to solid 4hi light.

I have 2 hi and 4hi, can hear the tccm click(checked for corrosion/loose connections at plug), can hear the encoder motor working. Vacuum lines are good, hold vacuum, vaccum switch good, locks the front axle, unlocks just fine...ive tried clearing the tccm codes...

I guess where im at now is, can the encoder motor work for 2hi, 4hi, but not 4lo? Could it be the selecter switch on the dash even though it blinks when i press the 4lo button?

Thanks in advance to all that even ponder my problems,
Brent.

 

If there is a problem with the encoder portion of the encoder motor, it definitely could prohibit a 4LO shift. Channel B is only active in 4LO so if there is a problem with the hall effect sensor that triggers channel B in the encoder motor, a problem with the wiring between the encoder motor & TCCM for channel B, or a problem with how the TCCM senses channel B inside the TCCM, 4LO would not engage.

Before you cleared the TCCM codes, did you record what they were?

 

Sadly no...i just took out the fuse and disconnected the battery for at least 30 minutes,then cycled through turning the key the required 5 times. I just read through the diagnostic procedures again, and am doing it, after i start it and try switching in and out of 4wd a few times so it will store the codes that that have to be presented multiple times in order to pop up.

thanks swartlkk for all the help u've given to others, and ur dedication to all the blazer lovers out there!

Well, started the truck, and tried cycling through 4wd and then back to 2hi. Turned off the truck, waited, and restarted it and cycled through my push buttons again. THEN, checked for tccm codes off pin 13 as per diagnostic procedure and got noi codes....

 

It may take a while to get the codes to set again.