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'?

The PCM provides the ground for the horn.The drive lube and low oil also go thru the PCM.

and the warning horn as to be hooked and working as well.

I traced the tan/blue from the male side of the cannon plug and it goes to the pcm as you said. It sounds more like a bad/loose connection then something wrong with the pcm? I verified the horn works and have continuity from the horn to the pcm...also power from the ignition to the horn. I will be putting my motor back in soon then I can see if the drive lube monitor will sound the horn every time or not