Test B: The Vehicle Does Not Shift Between 2WD and 4WD Modes Correctly

PINPOINT TEST B: THE VEHICLE DOES NOT SHIFT BETWEEN 2WD AND 4WD MODES CORRECTLY
Refer to Vehicle/Diagrams, Four-Wheel Drive System for schematic and connector information.

Normal Operation
The mode select switch communicates the operator's choice to the four wheel drive (4WD) control module. The 4WD control module then controls the transfer case clutch and transfer case shift motor as necessary. If the vehicle is not responding to the operator's intentions, systematically check the necessary inputs and outputs of the 4WD control module, components of the transfer case and halfshafts. Check all circuits for opens and shorts to power or ground.

Possible Causes
^ Transfer case
^ 4WD control module
^ Front axle assembly
^ Circuits:
- Battery circuit SBB27
- Ground circuit GD161A (BK/YE)
- PDB fuse 27 (20A)
- CCF13A (WH/BU)
- RCF13A (WH/BN)
- CCF14A (GN/OG)
- CCF15A (BN/YE)
- CCF16A (VT/GN)
- CCF17A (WH/OG)
- RCF09B (BN/WH)
- CCF07A (BN/GN)
- CCF08A (GY/OG)
^ Mode select switch (MSS)

B1-B2:

B2-B4:

B4-B6:

B6-B9:

B9-B10:

B11-B15:

B15-B19:

B19-B20:

B20-B21:

B22-B24:

B24-B26:

B26-B31: