Motorcycle engine oil lights indicate the pressure in the engine's oil system. Consisting of an indicator light, oil pressure sending unit and associated wiring, there are several ways that the light can give a false reading. Burned out indicator lights, corroded light sockets, bad sending units, broken wires or corroded connectors may all give a false "good" indication by preventing the light from coming on. Bad sending units, short-circuited wires and corroded or persistently wet connectors can give a false "bad" reading by leaving the light on.
Check the engine oil level and add oil if it is low. Turn the key to the "Off" position, then remove the negative battery cable from its post.
Remove the instrument cover panel and check that the light bulb is good. Check for continuity through the bulb with a multimeter. Inspect the bulb contacts and socket for signs of corrosion or arcing. Clean up any problems with emery paper and light pressure. Replace any severely corroded or burned components.
Remove the wires at the oil pressure sending unit (either unplug or unscrew) and inspect the connections for corrosion or arcing. Clean up the contacts with emery paper.
Perform a continuity test on the negative lead going to the switch. Test between this wire and the light socket to insure that it shows continuity to the negative contact in the socket and not to the center "hot" pin. Lack of continuity to either point indicates a broken wire in between. Continuity to both points indicates that there is insulation breakdown at some point and that the wires are shorted to each other. Inspect the wiring harness for pinch points or any obvious damage.
Test the sending unit for proper operation. Place the multimeter probes onto the two connectors and verify that there is continuity. Replace the battery negative cable onto its post and start the bike. Test the sending unit for continuity again. The meter should read no continuity or infinite ohms of resistance. This indicates that the switch is working properly. Turn off the engine.
Remove the sending unit with a pair of pliers and install an oil-pressure gauge. Start the engine and observe the oil pressure coming up. Refer to factory specifications to insure that the system is generating sufficient oil pressure. Lack of sufficient pressure at this point indicates a problem with the oil pump or some sort of internal leakage.
