I know this is a Blazer forum but I need some help with my 94 Sonoma. This truck is a 5 spd model. GM was in the changeover process at this time with the S Series trucks

Last winter my 4x4 went out. It does the blink thing on the buttons. It will shift into 4Lo but both 4x4 buttons stay lit. It is very hard to get it back into 2 Hi, I have checked the front axle and its working properly. I have checked the connector at the encoder motor and all looks good there. I have manually shifted the t case and all works good there as well.

What I need is some troubleshooting info on this OBD1 system. All the info on here is for the OBD2 systems. The TCCM is different on this truck. There is a single orange wire coming off of the TCCM. There is no connecter that I can see for testing. I don't want to declare the encoder motor bad as it does move back and forth. Also GM put those nasty security screws in the encoder motor and I cant find my security torx head bits.. So my question is is how can I check the TCCM and encoder motor to see which one is bad. Any and all help will be appreciated.. I could always pull my encoder motor off of my 96 and try it on there I guess. But Im trying to get by doing as little dismantling as possible.

 

Check out the article in the Tech Article (DIY) section by error_401. Should answer all of your questions.

 

I looked at the article Kyle pointed me to, its a good start but this morphodite truck is basically a 93 S10 with a later model body on it. Half the running gear is 93 the other is 94ish..

I took the encoder motor off of my 96 Blazer to check it and it does the same thing that it was doing before. Just clicks and the reverts back to 2HI. So I ruled out the encoder motor. That leaves the dash switches and TCCM. I swapped the dash switch out and its not the problem. I pulled the TCCM out last nite and its RUST covered. I pried up the tabs holding the case together, and it looked ok inside. However looks can be deceiving. The wiring all looks great with no corrosion in evidence.

When I push the clutch in and try to change ranges the 2 4x4 lights lite up together and blink 4 times. You can hear the encoder motor trying to shift but nothing seems to happen. The article I have is for the OBD2 system as I dont have that connecter in my truck. I have the old style rectangular connecter. I believe its called a ALDL connector.

So I'm gonna have to call the TCCM bad. According the the info I have 4 blinks means a Ram/Rom fault. So it's off to the salvage yards for another.. I dont have a printer atm to print out the voltages to the pins so I guess I should get one before condemming the TCCM.

Any thoughts on this are greatly appreciated.