First off, i'm new here and i have searched everywhere for a similar problem but have not found one so i apologize if this has been answered before

So i bought a 2000 Blazer with the Trailblazer trim and the 4X4 was working when i bought it but after i bought i tried it again and it worked once until i shut the engine off and started it back on. Now none of the orange lights (the ones that show what is selected) on the 4X4 selector turn on, only the text lights up and the "Service 4WD" light is lit on the dash. I checked the fuses and they aren't blown. The previous owner changed the selecter buttons and i cleaned up the little oxidation on the TCCM pins but it still doesn't work. Has anybody had this problem before? Becuase right now i'm thinking the TCCM is bad. And what else should i check?

 

As stated in most all of the threads which have "Service 4WD", you really need to get the TCCM scanned for codes as it could be anything; encoder, speed sensor, TCCM, etc. It takes a full feature scan tool capable of bi-directional controls to pull the codes from the TCCM. Without getting those codes, you will be taking a stab in the dark at actually solving the problem. How lucky do you feel?

When you cleaned the corrosion on the pins of the TCCM, did you also clean the mating terminal in the connector? These can often be worse than the pin in the TCCM. I have had luck slightly opening up the terminals after pulling them from the connector so that I could get inside and give all of the contacts a good, thorough cleaning. I have had some split and need to be replaced, but not many.

 

do you have the regular 4x4 with just hi, lo, and 2wd? if so you can pull codes your self with a paper clip on the data link connector or OBDII port as other refer to. you have to connect 2 pins (i forget which 2) in the connector together, turn the key to on dont start, the 4x4 buttons will blink the code for you

if you have the auto 4x4 then you cannot do this and you need to have it professionally scanned

 

Count the pins on your obd2 connector from left to right. On the 5th pin go directly down. Put a wire in that pin, put the other end on the E brake lever. That should be enough of a ground. If it flashes twice it will be your Encoder Motor. It it flashes three times its the Tccm.