Yes, the horn should be replaced with an idiot light instead. This way you have a code popping as if the battery IS low. It goes something like this. I have a 'threshold' and when it is met I blow the horn. If I have met another [planned by the builder] of the circuit board, that I can take a voltage number, send it to the 'threshold,' so this collapses and blows the horn-fandango, turns my idiot light on-fandango.
That's how you can play with battery voltage level to; I can ring your bell with a volt; because I am electrically handcuffed to a 'discharge;' to a 'threshold;' to a 'trigger' blowing horn. Make sense we diagnose the computer bike in this fashion?
Think toilet bowl tank:
1. Trigger is the tank's lever handle.
2. Discharge is the emptying of the tank.
3. Threshold is the water keeps coming into the tank but there it is stop by a threshold.
a. I flush the gray matter is the trigger.
b. the discharge is the volt sent in size so 1.2 gal right? 1.2v right?
c. we start all over is the crank comes around making volt and the float is the volt/reg controlling volts to gallons.
d. think out the ass so you come up with toilet to volts to flush to trigger to threshold to blow it out your ass goes the horn.