The brake vacuum pump connects to the rear of the right cylinder head on the Highlander. To begin work place jackstands under the vehicle and lift it while loosening the wheel lug nuts on the left front side. Unplug the battery negative cable then take off the left front wheel and inner fender panel to reveal the engine lower shield. Drain coolant from the engine and proceed with the process. On Highlander versions begin by taking off the wiper arms and motor parts then removing the cowl vent tray. Take off the components consisting of the air filter housing and throttle body. Take off the transaxle control cable from its top connection point then unfasten the bracket before removing the breather hose plus PCV hose and disconnecting the heater hoses from the coolant outlet pipe. Unfasten the hose clamps and remove all hoses from the vacuum pump. Disconnect the main engine electrical wires and safely move the wiring bundle off the pump. Take out the vacuum pump after you remove all the bolts and pull it from behind the right cylinder head. Also put in a new vacuum pump when there is oil leakage or when the O-ring gets broken. Coat vacuum pump O-rings and hole insides lightly with engine oil before positioning and fixing the vacuum pump coupling into the camshaft groove. Mount the vacuum pump with specified bolts then tighten them to complete installation. To access and remove the brake vacuum warning switch you must first remove the cowl panel followed by disconnecting the electrical connector from the switch while noting the cable orientation. Finally take out the switch from its grommet on the 
Brake Booster. Set the switch correctly on the brake booster facing upward at 11 o'clock when installed on top or downward at 5 o'clock in the bottom section.