I had it connected to the solenoid, but I will try to connected the ECM side of the same wire that goes to the solenoide, cause the solenoid is attched to the engine block so it suffer from vibrations... and if I connect it to the ECM it stays still...
must be a 3-4v led so it doesn't suck all the volts...
check it out:
i-vtec solenoid wiring help - Page 2 - 8th Generation Honda Civic Forum