on my '94 (square body) s10 blazer.. the manual says I can ground ODB1 pin J to Pin A, and the transfer case module will flash the lamps in the 4x4 switch to show the dtc's.. either 1, 2, 3 or 4.. .the one thing it doesn't mention.. what happens if there is no DTC? like the ECM will flash code 12 and nothing else if there are no codes..

I just replaced my 4x4 switch in the dash.. nothing happens when i hit 4x4.. but the lights do come on for about 2-3 second when i turn the key on, indicating the self test happened...I used myt tech-1 to activate the transfercase dtc mode and nothing happens.. i'm going to go through the rest of the pin point test today and see if I can figure out why i still haven't got 4x4... I know I made 4x4 engage using a test light on the harness.. b4 *Sigh*

 

Turns out my tech1 was not grounding pin j as it claimed it was. I jumped pin j to A ... And it gave me dtc codes 1 and 2. 1 is backup power failure (normal) and 2 is encoder motor fault. Im clearing the dtc codes and will see what happens... I might try to manually operate the shift motor to see what happens

 

Cleared rhe tccm dtc's. It will shift now but only between 2hi and 4lo. Still throwing dtc 2. Going to check the wiring then probably order a new tcase encoder motor.

 

This is a known problem with the encoder motor.

The fault #2 is telling you that the TCCM cannot properly determine if the encoder motor has properly shifted. After accumulation of so and so many faults, it goes into direct shift which is an emergency shift mode and only 2HI to 4LO will work. That's probably a safety measure to get you unstuck and home. Kinda limp-home mode for the 4x4.

I once fixed it by opening the encoder part and removing old grease that had the swipe arms float over the contact area instead of touching it. It held up for about two years, after which the fault was back. Replaced it with a Dorman replacement encoder motor. Has been working ever since. Maybe 10 years now?

I'll have a look if i can find the writeup. Found it:

https://blazerforum.com/forum/tech-a...-switch-29170/

 

right. I back probed at the tccm.. And according to this chart and the voltages i read, the motor either isn't able to go all the way into 2hi, or the encoder is wrong. The voltages match up with the 'between gears' line immediately above 2hi.