hi, i have a 2000 s-10 blazer with 4 button 4x4 (with auto) and nothing works in 4x4,dash buttons flash briefly when starting vehicle otherwise nothing.I located the tccm (15748800) and found it had corroded pins on both connectors, i cleaned them up and tested continuity (now okay).still no 4x4,i spoke to the shop foreman at the local GM dealership, he suggested changing the transfer case shift motor, which I did (very expensive and did not help).I have tried pulling the fuse to the 4x4 waiting 3 minutes and replacing then cycling the ignition on/off 5 times to reset the tccm (another mechanics suggestion),this did not work either. I went to auto salvage and got a different set of dash switches (no change).still nothing lights on the dash buttons, I am an electronics tech. so i checked the tccm for voltages and most pins have voltage readings,however the relays never close,am I dealing with a bad tccm or could some other problem cause this condition? could a vacuum problem cause this or would I still have dash buttons lighting with a vacuum problem?any help will be greatly appreciated,reply to thread or email me directly,thanks,jodyc. p.s. I have read through all the treads on nv/np 236 and i seam to have the same problem as "the beast" in his thread "1999 4wd not working" however i have not been brave enough to invest in a new tccm yet, also "mikeymo67" has a problem similar to mine also.From what I have read I expect my next step is to have the tccm codes checked? the nearest tech2/GM center is 50 miles away, do you think it is wise to drive her that far with this problem?

 

One simple thing you can check is the connections at your encoder motor if you haven't already. Mine had a bad one at the 4 wire block that needed replacement.
Also, have you checked for correct operation of the vacuum actuator?
It's under the battery.

 

having the codes will take the "throwing parts at it" factor out of the picture. you will be able to whittle down a lot of the stuff that could still be going on. I spent almost a year (off and on) throwing time, $, and parts at a problem that turned out to be something as stupid as my sending unit being plugged into my TC and my TC being hooked up to my fuel pump (wtf, right?).
*BONUS* you can get a new TCCM for like $60 shipped via ebay if you decide to go that route instead.
really a 2 hour drive and a half hours labor to narrow the problem down to a fine point should be worth it to you if that is the only option.
*try calling around to local shops/4WD specialty places and see if any of them pack a techII. doesn't have to be a GM dealer reading the codes

 

Pull each wire from the electrical connector one at a time. Clean the contacts thoroughly and stretch them a bit to make for tighter contact before putting that wire back in. Work through all of them. Your problem may be continuity at the connector. Corrosion can cause the terminal on the end of the wire to spread and lessen the contact force.

Aside from that, you really should get a scanner on it before you wastefully throw more parts at it.

 

thanks for the quick reply guys,i'm so glad
i found this site.today i checked for vacuum at the actuator,there isn't any but i'm not sure there should be if my tccm,etc are not working and asking the solenoid on the firewall to open applying vacuum to the actuator?
I will reclean each tccm connection individually but as i mentioned before I have checked continuity for each connection (from the wire side of the connectors directly to the pc boards solder joints) they all checked okay.I'm in rural new brunswick, canada and none of the local shops have a tech2, but i will get an appointment with the GM center in the city to check the codes.If you can tell me where I should or shouldn't have vacuum if my problem were elecrtrical that would be a great help as
i am not sure if the lack of vacuum to the actuator is relavent at this point (because nothing is lighting on my dash buttons just the "service 4x4" indicator)? thanks for your help guys, i really appreciate it.

hi,thanks for the info,I would be interested in knowing were these $60 tccm's are? i've been searching ebay and found nothing even used under $200us and new ones are running over $450 us.If you can tell me a sellers name or an item # for the ones you are referring to I would purchase one becuase mine definately has some corrosion damage (which i cleaned as best as i could) and may very well be a large part of my problem.Even if I get my 4x4 working I won't put much faith in my old tccm.Thanks for the quick reply and for any future help,regards,jodyc.

Thanks for the great advise, are you referring to the connectors at the tc shift motor because in my earlier reply i was thinking you were referring to the connectors at the tccm (which i had already cleaned and continuity tested).Please clearify that for me and thanks again for all your help.

 

If you do not want to go back through the terminals at the TCCM, that is your choice. But if you would re-read my reply, you would see what can happen when/if corrosion spreads the terminal apart. Continuity checking with the plug disconnected does not mean that the connection is actually tight (and continuous) once reconnected.

And yes, you should clean all of the electrical connections at the various components in the system (switch, TCCM, and encoder motor).

 

Do you have an update? I'm really curious because my 3 button system went dark today. It flashes briefly at startup, you can hear a glovebox relay click then the button lights go out. It has been working great until today.

Thanks,
John

 

Different setup all together. The troubles of the NV233 have been fairly well documented. A few key searches should turn up a number of things you can try. If you still have questions, post up a new thread on the topic.