Have an 03 Dodge Ram 1500 4X4 5.7 with headlight issues.  Initially had intermittent lights, but now neither high/low beams work on either side.  There is an HID kit installed.  
I’ve read there are problems with the FCM and PDC, so I’ve been focusing in that area.  Replaced the FCM, but no luck.

There is power at the FCM. Checked the pins from the FCM to the headlight connector, and the wires are good.  Checked the ground pins at the FCM through the PDC, and the grounds are good.  
Parking lights and fog lights turn on, but no headlights.

Checked for 12v at the headlight connector with a digital meter, and the voltage goes to 1.5 then drops out.  If I check the headlight connecter with a test lamp, the test light turns on and then off and back on again repeating this.  

Why would the voltage cycle with the test lamp?  Is the FCM looking for a specific resistance and then dropping voltage when it’s not there? Or should there be constant 12v?

I’m waiting for an appt at the dealer to run a scan.  I know the scan tool can also check the data bus communication.  That’s the only thing left I can think of unless it’s the HID kit.  I haven’t done anything with the HID kit because the initial low volts using the meter.  

I’m I missing anything, or do you have any ideas of what else to look at?

I'm guessing the HID kit is an aftermarket.
Maybe the ballast is going bad or a resistor/relay that stops the flickering some vehicles have.

Yes aftermarket HIDs.  I initially thought the HId was good because the low voltage at the connector.  Now I'm not so sure