Quote Originally Posted by jab351w View Post
It's the other way around: for the brake lights the switch is normally-open and closes when the brake pedal is depressed.

Based upon the highlighted portion of the schematic, the ABS module wants the opposite to happen: the switch should be closed when the brakes aren't depressed (12V to module) and open when they are (open circuit to module).

If your brake switch has both normally-open and normally-closed contacts, you can connect the NC contacts to the ABS module and the NO contacts to the brake lights, with +12V feeding both.

Assuming the 12V source feeding the switch is hot all the time this means that the ABS module will see 12V all of the time when the pedal isn't depressed, even when the key is off.
This differs from the OEM application shown in the schematic where the 12V feed is switched by the PCM power relay.

This may or may not cause the ABS module to remain active all of the time and increase its standby draw on the battery. If it does you could add a relay that's activated in start/run to replicate the function of the PCM power relay and feed the NC brake light switch via that.
thanks - I tested continuity with my other brake/clutch switch since it's extra (Coyote includes it's own clutch switch)

  • the two prongs closes to the button are NC
  • the two prongs at the end of the switch (furthest from the button) are NO


it seems I could wire both the brake lights and the ABS sensor to the NO prongs then, no need for a 2nd switch
BUT in the FFR setup the button is always pushed at rest, so I probably can wire to the NO ports on the end of the switch - does that make sense?

I guess my next determination is to figure out if I should put in a relay to the ABS unit and use the brake switch as that trigger for the relay?