Changing strategy for pin B20 engine shutdown.

[Rides]

Hi guys. OK I'm wiring up an Electromotion engine cut/shutdown system. Now the system rests at 12V then when triggered drops to open circuit. What I'd like to know, can I change the strategy with SmartWire to kill with negative/open circuit instead of ground to earth? I know I can do it with relays, but that defeats the reason for SmartWire and also more fail points.

[300mphvette]

I have the same issue. I need to wire an emergency shutoff switch that opens a circuit when it activates.

I have a theory that if you were to add about a 1K Ohm, 1/2 watt "pull-down" resistor between the B20 pin & ground, it'd overcome the pin's built-in pull-up resistor, changing the pin's behavior, making the SmartWire default to a shutdown condition unless the B20 pin has 12 volts applied. You'd then just need to wire 12 volts from a battery source (or, in your case, the ECU) to the B20 pin to allow the SmartWire to operate. Remove that 12 volts, and the SmartWire should shutdown.

Your 12 volt signal source would have to be able to provide 12-15 milliamps of current, which shouldn't be a problem.

This is only a theory, that I haven't tried, yet. When I do try it, I'll pass on the results. Keith