[RayLivingston]

For as long as we've had our '07 335i, it's had an annoying problem - it ALWAYS thinks the right front side marker bulb is bad. Until recently, it was a minor annoyance - we'd get the error on the MF display every time the engine was started. But recently, it's started giving us the warning at random times while driving, at a rate of several times per hour. There is NOTHING wrong with the bulb or socket. I can swap the whole light fixture from left to right, and it STILL complains ONLY about the right side light.

Is there ANY chance simply putting in new bulbs will solve this, or is there a problem in the lighting controller? What is it actually testing for to determine the bulb is bad? I really could not care less whether those lights work or not, I just want to stop getting the nag all the time. Is there a way I can trick it into shutting up, even if it means the side markers do not work?

[PhaseP]

It tests the lights by turning on the voltage on them for very short time and measuring the current. It turns them on shortly that bulb doesn't get enough time to really light up, if bulb was turned off. If no current or not enough current it will consider bulb is out. It does this on start up and then at some regular interval as car is on. This is the case when the bulb is not turned on. If the bulb is turned on, then it monitors the current flowing on it as it knows bulb should be on and drawing current.

You need to look at all the electrical contacts and connections from the socket back to computer. Something likely is not making good contact and as car shakes going over bumps it gets loose and then makes contact again. If you see green copper corrosion residue, or blackened hardened plastic showing high heat you found your weak connection point.

I had this with my turn indicator light on one of them, but in my case it was the socket not making good contact with the bulb. Had cleaned the bulb contacts with contact cleaner, bent them a little further so they press firmer on the bulb and it had fixed it. Later on I found out BMW was recommending to replace those sockets with newer part number ones.
But in your case if you switched the socket between right and left and it still stayed same, then I would check connections behind the socket and back.

[RayLivingston]

Any idea what connectors/etc. exist between the socket and the controller, and where they are located? I don't even know where the "footwell" controller is...

[PhaseP]

This gives how to access to footwell module:

https://www.bmwrepairguide.com/bmw-f...2013-3-series/

From my Bentley manual the "H8a Direction indicator light repeater, front right" socket is called X390, and the brown 0.5 mm2 wire from it goes to ground at x166 grounding point. X166 grounding point is on the right side (when sitting in the car looking forward, i.e. passenger side) inside the engine bay close to where the coolant reservoir is, at the fender side inside, from the picture I see.
The other wire from the socket is blue/yellow 0.5 mm2, and that goes into footwell module pin 11 at connector X14260.

"H9a" is "left" direction "indicator light repeater", its brown wire goes to x165 grounding point which is at driver side inside engine bay on the left fender side (driver). Its blue/yellow wire goes to footwell module pin 44 at connector X14261. There are multiple connectors on footwell module.

The socket connectors may have corroded too, again anything greenish is indicator of corroded copper. Anything brown or blackish hardened plastic indicator of not good connection causing heat.

[ky0u]

RayLivingston quick thing you may wanna check as well, idk what the bulb connectors look like on the e90, but on my e92, its held on by a simple metal bracket that you twist the bulb into. Overtime, this bracket gets a bit loose or wears out to the point where the bulb can wiggle enough to move out of contact.

I had issue with the same error light intermittently turning on until I went in and flexed the bracket so the bulb seated more securely. It hasnt come back since then

[UK_Nomad]

Had the same phantom warnings about the rear foglights in my E93, fixed by removing the bulbs and cleaning the contacts in the bulb holder and gently bending them so they hold the bulb firmly. Smear the contacts with petroleum jelly before refitting to stop future corrosion.

[RayLivingston]

Thanks all! I'll give those suggestions a try, and see what happens.