Have a scanner read the codes, if you want more specific answers.
Some customers may comment on intermittent illumination of the "Service 4WD"
light. Upon investigation, the technician may find DTC C0374 set. The
customer may also comment on intermittent erratic operation of the 4WD or
AWD system after driving through rain/snow or simply going through a car
The speed sensor signal may have become corrupted. Possible openings in the
speed sensor wire insulation (twisted pairs) can allow water intrusion.
Also, wire connections contaminated by water may result in short circuits
and erroneous speed sensor readings. This most often occurs on the rear
speed sensor circuit.
Inspect the wiring harness to the transfer case speed sensors.
On the full-size pickup and full-size utility models, replace the 2.2 m (88
in) pigtail harness that runs from the C151 connector under the hood to the
The smaller transfer case harness splices into the larger chassis harness a
few inches in front of the crossmember. The chassis harness routes along the
left side of the frame under the driver door area. Use nylon tie straps to
secure the fabricated harness to the main chassis harness between the
Do not over-twist the two wires in the replacement harness.
Check all grounds for poor connection. Also inspect the engine grounds, as
other components grounding through suspect grounds can then seek other
ground paths and interfere with transfer case operation. Battery cable
engine grounds as well as grounds located on the back of the engine cylinder
heads and engine block are possible sources of this concern