I've got a 2004 with HID lights on it, just wired through the low beams. Both headlights have been only working off and on. Sometimes one will be out, sometimes that one will start working fine and another one will go out. When one isn't working, it keeps trying to turn on every second or so. So I put a test light on it, and it turns out that the power coming to the non-working headlight is pulsing on and off.

After looking through the manual, it seemed like the front control module might be the most likely culprit. If it was the switch or something, both sides would be tied together and would either work or not work at the same time. Right? And what kind of short or other physical problem would cause the power to pulse consistantly like that? It had to be the FCM. So I replaced the FCM. It wasn't the FCM.

Any ideas as to what else could be causing this? As far as I can tell the head lights are the only things not working properly.

 

I believe you have to wire relays in. The FCM will only carry so much amperage before it turns it off thinking there is a short in it.