2009 Toyota 4Runner Owners Manual - Page 202

2-4. Using other driving systems Full-time 4WD models H4 (high speed position) Normal driving on all types of roads. L4 (low speed position) Driving requiring maximum power and traction such as climbing or descending steep hills, off-road driving, and hard pulling in sand or mud, etc. The 4LO indicator will come on. 178