The positive wire on the right trunk lamp (grey with black stripe) is not receiving signal from the SAM which is also throwing error 90B2 -component E18/4 Right Trunk Lamp is faulty of the line to the component has a short circuit or open circuit. I tested voltage at where the wire is damaged but it's showing no voltage at all.

Unfortunately the harness contains TWO additional wires with the same gauge and colour and hence can't tell which one is which so I could test it at the rear SAM and determine whether the issue is in the wires or the SAM (which might need replacing anyway if I was going to retrofit rearview camera and motorised boot lid?)

May someone please hook me up with the wire diagram for that?

Thanks!

I should also ask, any idea why some w221s have the rear quarter panel cabin vacuum vents with a wire/sensor (e.g. A2218200775 )

I was looking thru this: https://charm.li/Mercedes%20Benz/201...d%20Diagnosis/

Look under Lighting and Horns.




Looks like its the K3 connector at the sam. 2 and 18.

Tim, share more?

USA cars seem to get an antenna there on both sides (on the inner rear wing vents) - for what I don't know. A while back I wondered what the car uses for BLIS (blind spot assist)
Mine has nothing but loads on USA ebay for sale with wiring using a fakra connector as far as I can see ? so an antenna of some sort - I wonder if its for the "I crashed please help stuff" that's so prevalent in USA ?

Could be an antenna at the vent. I looked up that vent part# and a listing mentions antenna.

I guess there are different options with USA and even Canadian. Antennas in the trunk, top of the rear windshield, the obvious antenna on the roof which I think is GPS. Tire pressure antenna also somewhere in the trunk maybe under the spare tire.

Can see some of the different antenna options and where they are located in the link: https://charm.li/Mercedes%20Benz/201...d%20Diagnosis/

Probably different options just based on year. Look under Accessories and optional equipment > Antenna.

Thanks heaps Tim.

I'll have a go at the SAM diagnosis tomorrow after I finish with the dashboard speaker replacement. @Minh (see https://mbworld.org/forums/s-class-w...r-removal.html ) did that at few years ago. I got a similar tool (with an extended reach) and still it was very difficult to reach into the two bolts closest to the windshield. I've decided to remove half the dashboard, it's much easier. The only thing that didn't go as planned was the trim panel below the cluster/comand screen A2216890908 7241 - the notch for its sole screw cracked and broke off despite being uber careful. So back to the wreckers tomorrow - although it can be ordered in from MB Germany for about a hundred. Just realised how poorly the dashboard was put together, MB ought to have added more insulation and padding around the fittings, particularly the top dashboard which creaks like 90s Renault interior plastics.

So these vents are useless in the case in an EU-spec car, great to know.

The vents function. They just happen to have an antenna in it. They act like dryer vents and allow air to escape when the doors and trunk lid are closed.

I found a used one with the vent stuck open:

Blind spot warning is an extension of distronic plus. It uses the distronic plus sensors in the rear quarter (bracket mounted to the bumper shell support frame) to detect vehicles approaching in the adjacent lane. It's a facelift only system but the only extras will be software, the mirrors with the indicators and another wire or two between the mirror and front door modules.

Incidentally, a late facelift W221 with electric power steering, lane keeping assist, road sign camera and distronic plus has everything required to be self driving.