4x4 mode shift problems

My 93 sonoma no longer shifts into 4HI. It was shifting fine awhile back but no longer does. It will go from 2HI to 4LO but not 4 high. I get a trouble code of a 1 and 2 from TCCM. I have a factory service manual but, where the heck is the ECM at!? I need to get to the TCCM to do some wire troubleshooting. No blown fuses. I have an electronic shift transfer case, model 233.


I tried to think of what I did different since it was last known working fine. I can only think of these...

1 Changed front shocks
2 Replaced courtesy light bulbs with LED lights (blew a fuse while
doing this and had to tug on wires a bit to get enough length to
solder wires, with shrink tubing).

Any help is greatley appreciated.

I'm not sure about 1st gens. But the ECM on the 2nd gens I believe is on the right side of engine compartment. & the TCCM is under the front right kick panel. Does your truck have vacuum pod. I just fixed a bunch of burned up vacuum line on my 97 Blazer 4x4.

Not sure about 1st or 2nd gen but from what I understand, the tccm is on the back of the ecm. I see nothing in the engine compartment that looks like this. It does have an actuator pod, it is under the battery.

Not sure about 1st or 2nd gen but from what I understand, the tccm is on the back of the ecm. I see nothing in the engine compartment that looks like this. It does have an actuator pod, it is under the battery.

Did you look behind the kick panel??
Might do a search. I have had to do a bunch of that the last day.

Gonna look behind the kick panel today. Ill post back.

Gonna look behind the kick panel today. Ill post back.

Please do. We can all learn that way. I'm fair up on certain areas of the Gen 2s but have never messed with the 1st Gens.

Looked behind the kick panels but found nothing. If I knew how to attach a picture to a message I would take a picture or two of the engine compartment and maybe that would help.

On a new development, I pulled the eccm fuse for 3 minutes (according to shop manual) to clear the codes and the thing started going into 4HI and back to 2HI. I could do this about 5 times till the code 2 set and it stayed in 4HI. Pulled fuse again to get it back to 2HI so I wouldnt eat gasoline. From all this, can I assume the transfer case motor is good?

Well I found the ECM and TCCM. I went to the salvage yard and Went through 4 trucks till I found one that wasnt missing a control module. Salvage yards are great. You can tear stuff apart and not worry about breaking something. I got a control module off a 92 S10. I hope it interchanges. Same engine and electric shift setup. The ecm was behind the glove box. The TCCM along with the speed buffer are attached to each other. It can be pulled down from underneath after taking off a trim piece. Bad storm right now so Ill try it tommorow.

Looked behind the kick panels but found nothing. If I knew how to attach a picture to a message I would take a picture or two of the engine compartment and maybe that would help.

On a new development, I pulled the eccm fuse for 3 minutes (according to shop manual) to clear the codes and the thing started going into 4HI and back to 2HI. I could do this about 5 times till the code 2 set and it stayed in 4HI. Pulled fuse again to get it back to 2HI so I wouldnt eat gasoline. From all this, can I assume the transfer case motor is good?

Code 2 is a encoder motor fault.
The PCM is behind glove box area.
The TCCM I have not found yet may be center of dash area.
But I would work on the code 2 encoder repair flow chart.
Let us know how it goes.

You know, I checked the codes again and all I got was a 1 code. Followed the flow chart and ended up being the transfer case control module. I put it in and out of 4HI about a dozen times while in park. Took it for a ride and went in and out of 4HI a couple times and even tried 4LO while driving and it behaved properly. No more codes. A little bit of trouble shooting, 10 bucks at the salvage yard, and a little time well spent. Well see how it acts over the next week.

Glad you got it repaired. It is a good feeling to have things working correctly.