496 key on beep
 

Last summer the single beep when I turn the key to the on position was random if it worked or not. It would always start up fine and did not have beeps while running. I put 12+ directly to the horn and it works, I have also checked continuity on the purple and tan/blue wires that goes to the horn, from the key to the cannon plug and all checks out OK on the 'boat' side of things. I know the horn sounds when the tan/blue is grounded, either from a fault code, low drive lube or low oil pressure, All while the motor is running. And the purple has 12+ whenever key is 'on'. My question is, what grounds the tan/blue wire when the key is turned to the on position for a quick 'beep'?