Service 4x4 light stays on

My 99 blazer service 4x4 light would come on and off through out the day but now it stays on. I think it is a sensor but which one and where? How do I ckeck it. Help! I'm trading this in for a newby soon. Thanks

My 2000 Blazer began doing the same thing, the light would come on sometimes, sometimes not. Finally it came on and stayed on. I took it to the Chevy dealer this morning. According to them, my transfer case shift motor is out and the cost is over 800 dollars to fix. For your sake, I hope yours is something simpler.

1st Check vac actuator under battery tray for tears, or leaks, and that the vac hose is connected. Replace if found

2nd Check vac hose leading from vac actuator to vac switch on transfer case for cracks and dry rot. Replace if found.

3rd Check remaining 2 hoses from vac switch on transfer case for dryrot or cracks Replace if found.

If all of the above are fine, disconnect your negative battery cable for 1/2 hour then reconnect it. If your 4x4 works after that you probably have a failing TCCM (Transfer case control module)

If that doesn't solve it, it's most likely the encoder motor

Rlith is this for a 2000 blazer (your list) i know my 91 has the vac on the trans case with hoses but i do not see this on the 2000, there is a vac thing in the middle of the firewall the top has no vac when car is on but the bot dose is this normal

My 99 blazer service 4x4 light would come on and off through out the day but now it stays on. I think it is a sensor but which one and where? How do I ckeck it. Help! I'm trading this in for a newby soon. Thanks

Welcome on your first post on AF.
If you are going to fix it before you trade.
First thing check all fuses for power.
On a 99 with a 236 transfer case you will need a engine /transmission/ capable scanner to get codes that should point to the problem.
If you can get any codes post back code no.
MT

I had the same problem with my 2000 Chevy Blazer I talked to a dealer ship and they told me that 99% of the time it is just the dash switch. It costs about 35.00 mabe you could check that out.