Will not go into 4WD mode (4WD)

Probable Cause 

• Fluid level too low
• Incorrect fluid type

Remedy 

• Add recommended fluid - Refer to: Rear Differential Fluid Inspection and Replacement (4WD) Rear Differential Fluid Inspection and Replacement (AWD) 
• Drain and fill the differential with the recommended fluid - Refer to: Rear Differential Fluid Inspection and Replacement (4WD) Rear Differential Fluid Inspection and Replacement (AWD)