Problems with Passenger's Headlight
 

My friend with a 2007 SC430 is having a recurring problem with his passenger's side headlight. The HID lowbeam keeps periodically going out, then will start working again. When it isn't lighting up, it's doesn't work on either the lowbeam or the highbeam settings, while the driver's side lamp is working fine (driver's side lowbeam lamp is on with highbeam lamp when highbeams are engaged, and driver's side lowbeam lamp on as normal with lowbeam engaged).

He has replaced the passenger's side bulb with a Lexus OEM purchased from a dealer back in November which seemed to fix things for a while but now the problem is back again.

Any ideas what the cause(s) could be and how to troubleshoot? He previously owned a 2002 SC430 for 6 years and never once had any headlight issues or even had to replace any bulbs, and the 07 is giving him this grief now after barely 3 years of owning it.

HID Headlight -- sometimes great, sometimes dim, sometimes out -- diagnosis?

Dealer $120 labor. HID headlight costs an arm and a leg, even at Sewell

Hmm, so reading thru the thread, it seems for most folks just replacing the bulb cures this....but it hasn't for him, and the replacement was a Lexus OEM original from a dealer.

However, I believe he only replaced the one bulb that was acting up - do they have to be done in pairs?

And the thread makes brief mention of an ECU component for the lights? Could this be what is acting up with his car?

This could be a long shot. Why don't you swap the light bulb between them and see if the same problem still exist. If so, at least you know it's not the bulb. Could be the ballast or bad wiring harness then.

^^What he said.. Usually its just the bulb that needs replacing but if you swap bulbs and your experiencing the same symptoms then it could be a bad ballast.