how does the 4x4 engage??

[Mrooney322]

hi all,
over the summer i did the BWM all has been good up until recently. with all of this snow i have been noticing that the transfer case is not engaging the front axle and i am constantly in 2WD. with this said i have a 2004 explorer 4.0 V6. my question is how does the PCM know when to engage and disengage the front axle. i know that it could be something as simple as a bad splice i made and i am checking all of my work that i can, weather permitting. 2/3 of my ABS sensors are shot and i was curious if they were used in determining wheel slip to engage the 4X4
any input is greatly appreciated, more snow this weekend, really need to jump on this problem

 

[corkey]

the abs sensors are used to tell the pcm that the wheel speeds are different, if they are not working than the 4wd won't either, it has to sense the wheel speeds

 

[Mrooney322]

oh i see, definitely getting on that this week thanks for the reply