Disconnect the battery negative terminal.
Remove the engine room under cover.
Drain the engine oil.
(Refer to Lubrication System - "Engine Oil")
Remove the oil pressure switch(A).
Tightening torque :
7.8 ~ 11.8 N.m (0.8 ~ 1.2 kgf.m, 5.7 ~ 8.6 lb-ft)
Install in the reverse order of removal.