Correct - the green lamp holder and dual filament is wrong for this car -needs to be replaced with correct lamp and holder.

As for the voltages (averaged from the PWM signal) it seems there are three different brightness level on the tails: -

Tails - about 5v on all four lamps
Normal Braking - about 10v on the lower lamps and 5v on the uppers (so no change on the uppers).
Hard Braking - full voltage on all four lamps. I think this is the feature known as adaptive brake lights. Hard to see happen as I think it requires the ABS to kick in before this mode fires up! :dunno:

Thanks for all the input, and the great info wpoll!

So previous owner put in a green socket, which is for pre-facelift and not needed for my car correct? So I just need to order a new white socket and we're all good to go.

This is what my two look like, bulbs have different location terminals as well.

Is 7506 the correct bulb for the white socket?

https://preview.ibb.co/novFHe/0884_B..._C92_A0_A3.jpg

Yep. 12v 21w bayonet. Level pins (not offset) at 180deg. :thumbup:

Thanks for the confirmation! Also, the green socket does work in my car, so I'll keep it as a spare.

The green holder is normally configured so that it won't fit in your car - the PO must have modified it in some way. The plastic bayonet pins are offset on the green one while they are opposite each other on the white one. Have a closer look. ;)

Hi SigBoi. So, I'm reading your post - as I"m having the same issue - and still am not clear on what socket/bulb should be used and where. I have an 03' X5 so that's pre-facelift, right?

I bought mine about a month ago, with the "Check Rear Lights" and "Check Brake Lights" like you. On my driver's side, there was a green and white socket, forget which was where. Yet on the passenger side, both were green.

Did you ever find anything that was a definitive source for both my year and yours?

I can't get rid of these "check brake lights" errors!

True that. I've tried multiple times and can't find any led replacements for bulbs that work properly.

From what wpoll said above, I think you're supposed to have all green for pre facelift, and I'm supposed to have all white. That should fix it, along with the cleaning of the tail lights for some who have burnt connections.

You two need to get together and do a swap!! :bustingup

A pre-facelift should be all green. An LCI (facelift) should be all white.

Check your build-date for info on pre/post-facelift etc. LCI builds are around 09/2003 onwards (i.e. MY2004).

But biggest giveaway is the headlights....

https://xoutpost.com/attachments/x5-...42471676_n.jpg

(image from Munkhtulga)

Thank you! Yeah, I'm definitely "pre-facelift". And this should be easy enough, (trial and error) to put ALL GREEN sockets or ALL WHITE ...but I thought it interesting, (mine had white & green on drivers side, all green on passenger), and that Pelican Parts - whom I find to be pretty accurate - showed the picture below with both green & white. Interesting?

Who knew tail lights could be so complex :-)