2003 Volvo XC70. Bulb failure low beam. Background; Alternator replaced after getting High Voltage pull over safely message, got Bulb failure low beam message shortly there after. Both low beam bulbs not illuminating, high beams okay. Investigation; Bulbs checked good, fuses checked good, relay/shunt replaced with ones from parts car that headlights were working on. No power at plug for lights. As far as I know car does not have HID lights. Stumped as to what to try next.

 

time to check the wiring diagram but the CEM may be in the circuit path for the low beams. The CEM has relays in it which may have fried in your alternator event.

 

to continue this saga I took the car to the dealership and they confirmed that it is a bad CEM and recommended XeModex a secondary provider/repair facility for major electronic vehicle components. XeModex didn't have any reconditioned ones in stock. Bought a PN matching one on ebay. Sent it away for cloning to XeModex. Plug the newly cloned one in and still the same result no low beam headlights. Stumped big time. Looking for other ideas on what could be wrong. At this point also thinking about powering the low beam headlights through the running lights. Advantage of doing it this way is they are still control through the ignition switch, but wondering if the extra draw on that circuit will cause other problems.

 

Do you have power at fuse B17/18 for the low beams? If not swap relay 2/62 with another of the same part number (on the CEM). If still no low beams - the shunt 20/27 - is there one of the same part number you can swap? And have you scanned the car to see if there are any codes in the CEM related to headlamps?

 

I have a parts car that has the same style CEM and had already tried swapping out shunt 20/27 but not know about relay 2/62. Thanks for the suggestion, will try that when I get back from a short vacation.

 

Finally got the chance to swap out relay 2/26, tried a few from my parts car. Still no low beam lights. Don't have the ability to read the "codes". At this point I was thinking of powering the low beam lights from the running/parking lights. Does anyone see a problem with this?

 

Issue resolved. it appears that during all my changing of relays and such both bulbs did "blow". After installing new bulbs everything is working fine. And yes, I was disconnecting the battery every time I did something.