I have a 2002 5.9L SLT and just recently had a left low beam go out with a lamp out indicator and an overhead message of left low beam out. The 9007 bulb still worked in high beam and the right low and high beam worked fine. When I took the left 9007 bulb out, one of the filaments looked broken. When I put everything back together, I put the right bulb in the left socket and now don't have any low beams. Voltage meter testing at the left socket revealed fluctuating voltages between 6 and 9 volts on the low beam wire when low beams were on and a steady 8.32 volts on the high beam wire during low beam use. This fluctuation changed to the opposite wire when high beams were used. Is this normal? Is it just time to replace both bulbs? What should I do next? Thanks.. tad

 

Ok,
So I got home after work and after $29 I got some help from ask.com tech Brad. He suggested a bad FCM because of the low voltage on the left side. Tonight, I checked the voltage at the headlight plug on both sides. On both sides, the low beam read 9.3-9.7 volts and the high beam read 9.8-10.5. Both sides read the same, but this seems awfully low. Is it supposed to be this way? I put new bulbs in and they work fine with no "lamp out". But I am still concerned that there might be a problem lingering somewhere. Any help would be appreciated.

 

Not sure what the issue is but yes You should be testing around 12v on Both sides high and low beam

 

In my case (2004 3rd gen with Hemi) it was a bad FCM.