4WD only works once the battery cables are disconnected.

[shukapuka]

'02 Ford Explorer Sport 4WD High & 4WD Low dashboard icons aren't illuminating. If i disconnect my posative battery cable and then turn ignition key and then reconnect cable i can sometimes get the icons to illuminate, which allows me to have both 4WD High or Low. Both Low & High operate fine and there is no problem with engagement or disengagement.Once the vehicle is shut off the icons will not illuminate again until the above mentioned procedure is repeated.

 

[BrooklynBay]

Welcome to this forum! I've moved your thread into the transmissions & transfer cases section.

 

[swetrid]

It could be the 4x4 control module.