my friend has a 03 dmax and the other day he was drivin it home and a code was thrown to servive 4wd but he was not in 4wd, then a little bit later it went away and didnt come back up. i know the change engine oil will pop up when it needs to be replaced, will it also do it for the 4wd also? or was it just a fluke thing that happened?

 

No its not like the oil, what will happen is that IF he tries to shift it in 4 wheel drive in any range it will either not go in or it will go in and not come back out. Now you can get the light if the switch isnt operating to but I would hate to have you tell him to engage it in 4 wheel drive because it is almost an act of god to get it back into two wheel drive, but it is most likely the Transfercase motor which is on the tranfercase and its black and a cylinder but for him to be sure its the motor he might need to engage it and see if it comes back out because if it doesnt then its the motor if it doesnt engage all its the switch in the cab or the actuator on the front axle. The price of a new GM Transfercase motor is around 400+ so try junkyards first and the actuator and switch are around 80-100 but i highly doubt its those

 

so your saying without even using it it just went bad? he was just drivin down the road normally in 2x4 and was not even trying to get it in 4x4

 

I have the same issue mine will read service 4wd every once in a while it flashes really quick. But I can put it in 4wd and use it and still get it out. If you get an answer on this let me know cuz mine is doing the same. Maybe it it is the transfer case motor.