4wd service light

ok so my service 4wd light keeps comming on and going off, sometimes it will stay on for a few days and then shut off, other times it will go on but if I shut my car off and then restart it, it will turn off again. I checked the fluids and there fine and I also checked the fuse which is good. Any suggestions, please help

Make and model will help us narrow down your problems, but i will take a stab in the dark at the more common issues -

There are two major parts that make up the pushbutton 4WD on demand system that are your most likely culprits. One is the TCC or Transfer Case Controller located inside the cab of the truck. THis module can suffer from logic lock or just get plain weak over the years to where it will not drive the Transfer Case Actuator motor properly. The latter, is located on the body of the Transfer case under the vehicle and this is what slips the truck into various 4x4 modes and 2x4 high range.

If you remove the negative battery terminal for 20 minutes and then reconnect it - and this as a result makes the problem go away - I am inclined to think it's the control module inside the truck's cab. If it continues, indicating a fault - then I would suspect the drive motor module on top of the transfer case.

If you have a '97 and later vehicle, such as a Bravada or GMC Jimmy with this trouble with automatic AWD/4x4 system, you may have to have the transfer case serviced with the proper GM AllTrack-II fluid. (It will be blue in color) This fluid like others can just wear out with age and time, creating all sorts of strange behaviors on and off pavement and in loose terrain or slick conditions.

Good luck and let us know what year/make/model you're needing help with and we'll try to help more.

Thank you I will try taking the battery out and seeing if that makes a difference, my car is a 2000 Chevy Blazer

See the 4wd info in the FAQ section - should help.

Mine goes into 4x4 and runs fin and then the service l;ight comes on and it will not go switch to any other mode. I can turn the ignition off and turn it back on and switch it back to 2x4 and the service light goes off. Some times I have to disconnect the battery to get it to switch back.
any idea which part it sounds like?

99 blazer with 4 button selector.




[QUOTE=wolfox]Make and model will help us narrow down your problems, but i will take a stab in the dark at the more common issues -

There are two major parts that make up the pushbutton 4WD on demand system that are your most likely culprits. One is the TCC or Transfer Case Controller located inside the cab of the truck. THis module can suffer from logic lock or just get plain weak over the years to where it will not drive the Transfer Case Actuator motor properly. The latter, is located on the body of the Transfer case under the vehicle and this is what slips the truck into various 4x4 modes and 2x4 high range.

If you remove the negative battery terminal for 20 minutes and then reconnect it - and this as a result makes the problem go away - I am inclined to think it's the control module inside the truck's cab. If it continues, indicating a fault - then I would suspect the drive motor module on top of the transfer case.

If you have a '97 and later vehicle, such as a Bravada or GMC Jimmy with this trouble with automatic AWD/4x4 system, you may have to have the transfer case serviced with the proper GM AllTrack-II fluid. (It will be blue in color) This fluid like others can just wear out with age and time, creating all sorts of strange behaviors on and off pavement and in loose terrain or slick conditions.

Good luck and let us know what year/make/model you're

Is there a 4x4 relay at all?

I honestly do not know. I've got a '95 with a floor shifter and thus never had 4x4 problems...yet. *crosses fingers*

Ok so I previously posted about my 4wd light going on and off, now it is just staying on, it has been on for a few weeks now. so I tried to disconnect the battery like you suggested, but there was no change the light is still on. grrrr it is soo aggravating. my truck is a200 chevy blazer, any other help would be reatly appriciated. Also one of the post mention about the TCC and how it canget weak or suffer from logic lock, if this the case how can i fix it??