2003 ST 4 Stroke 9.9/15HP Johnson outboards Service Manual, Page 73Get this manual
IGNITION AND ELECTRICAL OIL PRESSURE CIRCUIT
Testing Oil Pressure Caution System
ENGINE STOP SWITCH
Check: ContinuityInfinity
Air pressure gauge
Air pressure gauge Air pump AssyDigital voltage meter Tester selector: J +I-
(1 )Remove oil pressure switch(2)Connect air pressure gauge and pump
Air pump assy
Tester probe connection Probe Other probe Black Green