Serv 4wd

A warning light illuminated indicates that a diagnostic trouble code (DTC) is stored in a module. Testing must be performed to see what code has been set. Once you have the code, then you can drill down to the source of the concern. If the problem is not actively occurring, it may be more difficult to get to the actual source of the concern, but it is still the only thing you have to go on, and by keeping an eye on that area, whatever it is, eventually the source of the concern will be apparent.