2008 Toyota Highlander Owners Manual - Page 806

2-4. Using other driving systems n System malfunction l The downhill assist control system indicator does not come on when the "ENGINE START STOP" switch or the engine switch is turned to ON. l The downhill assist control system indicator does not come on when the "DAC" switch is pressed. In the above cases have your vehicle checked by your Toyota dealer. CAUTION n Conditions which may affect the downhill assist control system The system may not operate on the following surfaces, which may lead to an accident causing death or serious injury. l Slippery surface such as wet or muddy roads l Icy surfaces l Unpaved roads 208