To switch to four-wheel drive in a 2002 Toyota Tacoma, reduce speed to approximately 60 mph, and press the 4WD button. Press the 4WD button again to switch back to regular drive. These instructions apply to both manual and automatic transmission models.
For maximum control and traction in more extreme off-road driving conditions, such as driving through mud or sand, reduce your speed to 5 mph or less. For models with manual transmissions, keep your foot on the accelerator pedal, depress the clutch, and move the front drive control lever from H2 or H4 to L4. For Tacomas with automatic transmissions, stop the vehicle, and put it into neutral. Hold down the brake pedal, and shift the front drive control lever from H2 or H4 to L4.
Do not attempt to switch to four-wheel drive if the wheels are slipping or spinning. Wait for the vehicle to stop before pushing the 4WD button or shifting. The full instructions for shifting to four-wheel drive can be found in the 2002 Toyota Tacoma Ignition Switch, Transmission And Parking Brake PDF manual on Toyota.com.