Hello everybody, I have several problems with my manual R56 that I haven't been able to fix.
The first problem that arose was the tail lights wouldn't turn off when I took the key out of the ignition, and it seemed like there was still current going throughout the car because the cigarette lighter plug would stay turned on as well. And I noticed that the fuse box kept on making a clicking sound every time I would insert the key, press the Start button, and take out the key. The clicking sounds would always vary in longevity and I also started to notice that they were more noticeable when it was really hot outside. I would have to keep on turning the car on and off until everything was turned off.
Some time after my car would just plain out not start. No cranking, no nothing but the clicking from the fuse box. The battery was fine because everything else was on but it just wouldn't start. I would have to wait anywhere from 15 minutes to 2 hours, trying to start it, until it started like nothing had happened, and it mainly occurred when it was really hot outside. In the mornings and at night the car would start without any problems but that trend that it kept malfunctioning when it was the hottest during the day caught my eye.

I was able to take it to an independent auto shop and they were able to supposedly fix it. They cleared the codes for the right tail lamp, left side marker, pass seat occupancy detector, they cleaned the corrosion on a couple of pins from the BCM connector, disconnected the battery, and the problems seemed to be fixed.
I got my car back and it seemed okay, the clicking coming from the fuse was minimized to about 1 click every time i put the key/clicked the button/took out the key, and the car would start just fine.

Two weeks later and it's 37 C outside and the car won't start. I wait 15 minutes, temperature goes down to 34 and it starts again. The problem came back and now I think I'm certain that it has something to do with the temperature, but at the same time I have no idea. There's also times when it finally starts, but it immediately dies. After trying again it usually stays on, but it also sometimes dies again when I let go of the clutch.
I've looked at a lot of videos and other forums trying to find answers but no luck. It could be the BCM or the starter, or something else that I have no idea about, and the temperature could also have nothing to with it.
Any help would be greatly appreciated.
Sorry in advance for my low level ability in writing as well.

 

Just a long shot, but can you identify what is 'clicking' in the fuse box?

From your description, it sounds like a stuck relay - one that isn't engaging or releasing reliably, depending on the temperature.
It might also be the computer that the relay is connected to - more dirty contacts, perhaps?

I have a similar issue occasionally with the high-speed fan relay; the fan sometimes won't stop until I flick the ignition on & off a few times, or tap the relay.

 

 

I don't remember how I found the fan relay! Probably from the manual or maybe from this forum. It only happens occasionally & with the A/C on - flicking the ignition off & on stops it. I have an early 2002 R53 - quite different wiring.
A schematic should show you what the Start/Stop fuse is connected to - that should point you to the relay or device or computer that is acting up.

PS If the Start/Stop fuse is F36, then I'd look at the 'Car Access System' & 'Start Stop Unit' modules & plugs. It looks like 13 gray wires + 1 red on the SSU, probably a ribbon cable, 4 additional wires on the CAS.