"Ok...hers's the deal. I
"Ok...hers's the deal. I was wrong when I said earlier that the green light should light when you ground the yellow lead. The green light actually turns on when the ground is removed.
The oil pressure switch is essentially at ground when the engine is not running. The ground goes away when the engine is running and there is oil pressure.
If you do a test at the lamp module, you should have a ground on the black lead and positive 12v on the black/yellow lead when you turn on your key switch.
If you turn on the key switch and disconnect the yellow lead to the light module, the oil pressure light should come on. If it lights, reconnect everything and go back to the oil pressure sensor and remove that lead to be sure everything is ok from there.
If it does not, double check the overheat light by putting a ground on the red lead. If the red light comes on, then your module is probably bad.
If your still not sure, I am sure your local Honda Dealer would test it if you took the module in. We normally test these things for free as long as we don't have to climb up into the boat and deal with no/low batteries etc.
The test is on page 17-27 of the BF75A-BF90A shop manual.
I did this test on a module today and it took two minutes.
Sorry for the inaccurate information in the previous replies."