I just bought a 2004 L300 Wagon and did some major repairs to get it running well. I saw another post here about the interior lights not working but mine have me stumped.
The instrument lights, DRL lights and everything else is fine. I just can't get either the front or rear cluster of interior dome lights to come on with either the switches or door sensors.
I've taken the front cluster apart and verified I'm getting 12V to the metal strips inside. I've even taken the cluster out, sanded the metal contacts (in case of corrosion problem) and bench tested it. All lights come on and work as expected when connected to an independent 12V power source. But when replaced in the car, nothing.
Thoughts?

 

I’ll think about that and look up the schematic when I have time. I have a 2002 fsm set and the dome light wiring should be close. Sedan wiring runs down the passenger side A pillar to that side fuse box and harness.

 

The lamps work when you test them on the bench, supplying 12v to one side and a ground to the other. You're getting 12v to the lamps in the car, but is the other side of the lamp grounded? Use a jumper wire from a known good ground to the other side of the lamp cluster in the car to see if they light. You may have a bad ground wire in there somewhere.

 

 

 

The lights have a ground splice probably above the headliner near the right visor. I would remove the visors and drop the front of the headliner and look if nothing works. Do you have three position switches off, door and on? Do you have separate map lights that also don’t work? If so check the ground splice and behind the trim panel around the interior fuse panels.

 

I have an update. I thought I'd checked the fuses but in retracing those steps I noticed a fuse labelled BCM2 in the lower right corner of the fuse box. It was in fact blown and after replacing it my dome lights and visor lights are working again.
However in the wagon version there's a separate cargo area dome light which is still not working. Measuring the voltage in the connector to that one showed it progressing slowly from .5V up to a bit over 1V over 15 or 20 seconds. Not the expected 12V. I'll see if I can track down a grounding or some other issue for that circuit.