4 Wheel Drive/SUVs: four wheel drive, mode selector switch, gearmotor

Question
the four wheel drive on my 2002 explorer will not disengage but it will shift from four low to four high?

Answer
Aaron,
There are numerous components that can cause this problem.  The one that usually is the prime suspect, is the MSS (mode selector switch.)  It may not be making a good connection in the normal operating position, which could be due to a bad switch,  or faulty wiring.

It could be a 4wd control module also.

As there are several things related to this problem, I would purchase a repair manual for the Explorer as it will have a trouble shooting section and diagrams of components and wiring for testing.

If you can't figure it out yourself, you may have to go to a reputable shop and have it diagnosed with a scanner.

The following is a list of related components that need to be checked.

Four-Wheel Drive Systems - Automatic Four Wheel Drive (A4WD)
The automatic four-wheel drive (A4WD) system is an electronic shift 4X4 system that utilizes the following components:

   * transfer case
   * four-wheel drive (4WD) control module
   * mode select switch (MSS)
   * gearmotor encoder assembly
   * electric shift motor (part of gearmotor encoder assembly)
   * shift motor sense plate (part of gearmotor encoder assembly)

Early Build / Late Build Definition
Early Build - Vehicles Built Before 03/2002
Late Build - Vehicles Built After 03/2002

Carl