Hi The_Runner,

I've been going through the Courtesy Lamp Circuit regarding the D/S Door Courtesy light circuit and here's what I think would help you to isolate your problem! The "Left front door courtesy Lamp circuit" Begins & ends at the MB-ECU terminals FLCY(+) & FLCY(-)!

So to be sure what the trouble is, I would (using a test light or 12V Multi-meter), GND the alligator clip/NEG-side of your tester, and touch the copper terminal attached to the "PINK" wire and see if it's HOT; it should be whenever the driver-side door is opened!

Then, I'd check the terminal attached to the RED wire (GND-TERM) by feeding the alligator clip 12V (from another power source), and connecting the test lead to that copper terminal; you 'SHOULD' have 12V at that termination!

If you don't have 12V (GND) at the RED wire, then check the door courtesy light switch; this is where your MB-ECU courtesy signaling device is located. You could remove the door switch and use an Ohm meter or continuity tester to confirm, or condemn the door switch BEFORE Condemning the MB-ECU!

Obviously I do have the wiring diagram for the door lamps; my trouble is getting a url to share them as photos/jpeg. If you need to see them for yourself, send me a PM with your email address and I can email the two pgs to you!

And if you need to replace the MB-ECU Compu net, I do have a Brand New one, from Toyota, still in the original box... just let me know how you make out AFTER testing the door lamp courtesy circuit and we can take it from there! 'Best to you'

rig