Oil Pressure Switch Test

Remove the YEL/RED wire (A) from the engine in pressure switch (B).

Fig 1: Removing YEL/RED Wire From Engine In Pressure Switch
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Check for continuity between the positive terminal (C) and the engine (ground). There should be continuity with the engine stopped. There should be no continuity with the engine running.
If the switch fails to operate, check the engine oil level. If the engine oil level is OK, check the engine oil pressure is OK, replace the oil pressure switch (see Oil Pressure Switch Replacement ).