I have a 2003 e39 530i. The three lights come on 5 - 10 minutes. Of driving and stay on until the engine is stopped and restarted. I had an auto-logic scan that repeatly sourced the error to the brake pressure sensor. The Trifecta is neither triggered by bumps or use of the brakes, I suspect that the error count reaches a threshold and throws the fault.
I was skeptical because of all the reading about the Trifecta being a wheel sensor or the control module. Note speedometer and cruise control works. ABS brakes work as well.
I back probed the three wires going to the sensor. Violet/black measures 4.36 against Blue/Black and 5 volts against the strut tower nut. The Violet/Black measures 0.64 volts against the strut tower nut. (Interestingly the net voltage of the two wire is 5 volts.)
I measure the White/blue with no brake pressure and the reading was .64 volts. With some brake pressure the reading was 1.25 volts. And with a lot of pressure the reading was 2.5 volts.
So do I spend the $100+ bums for a new sensor or is there a furred trouble shoot on the control module. I think I remember a post maybe by Blue Bee pointing to two suspect so feet joints and others to the fine wires being lifted.