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BMW M3 E90 / BMW E39 M5 /BMW E46 M3 / E55 AMG W211
Electrical gremlins - the hunt is ON and you can help!
Hey Guy. You've all been great at helping me diagnose my WOT engine failure (investigation still underway), so to prevent unnecessary clutter in that thread, this issue deserved it's own.
Quick facts: Car was bough sight unseen, it has 266,000km, it's been enjoying a pretty good spa treatment lately with some much deserved maintenance including, plugs, engine mounts, Eurocharged headers, exhaust flanges and hangers, oil and filters, new tensioner, front ball joints, brakes, pads, wheels, rubber etc... w/ more to come...
Now there's 2 issues and possibly a third one with the car that might or might not be related to one another, and that's where you guys come in.
1) The rear headrests - when pressing the switch - only the passenger side drops. The center and left one stay up.
2) The rear shade was up when I got the car and the switch doesn't work. Either the motor failed, the switch failed or there's something happening in the electrical connections. I manually rolled it back down and lifted the rear deck a little bit to peek at the motor and connections.
3) See the cluster message I got last week, about the "Battery Protection Conven. Function Temporarely Unavaillabe". (pic)
In an effort to start finding the root cause of all this, I started at the back of the car, on the right side where the fuel pump relay and fuse ought to be (based on what I read), and to my surprise there was nothing there appart from a single relay. (pic) I continued on the left side where the fuse box is, checked all the fuses and relays... took a minute to look at wiring, watched for any disconnected plug. Found a couple plugs and wire that were tied together and not used but they seemed to be for an optional cd changer...
Got the rear seat out and side paneling in the rear door frame as well as the bottom door trim to expose all the wiring going trough there. All seemed okay except for one single orange wire with a weird OEM terminal on it - it was disconnected. There were others just like it and they were connected together in a small black enclosure. I fished around and found another one that came from the front of the car which was not connected, so I connected those two together as a test, changed nothing... Anyone care to say what these are for? (pic)
Long story short, I didn't find anything out of the ordinary or anything that would cause a malfunction. I also checked the fuses beside the dash and the front fuse box as well. So the problem is either in the switches, or hidden under the rear deck lid which I'll need to take out eventually I'm afraid...
Aux battery and main battery fresh? Take a look at the rear sam for any water damage, had some water intrusion issues on my w220 that gave me some gremlins.
BMW M3 E90 / BMW E39 M5 /BMW E46 M3 / E55 AMG W211
Honestly, I'm not sure! The main bat. is an aftermarket one which doesn't look old... Car starts great and doesn't seem to drop in voltage over a week or two without use... but I didn't test them... I will.
I’m not too well versed about the e55 but I know there’s an aux battery (motorcycle sized) by the cabin air filter. As far as gremlins.. its definitely one of the tougher issues to pin down, but I always start troubleshooting by testing power source first. For the rear head rests, when you hit the drop button do you hear them all release? See if you can have someone push down while you hit the release button. Rear sunshade, I would say it’s the motor but don’t know where to start trouble shooting it. As for the message, I think a battery change would solve it (see link below).
Those are fiber optic cables for audio system. Extra ones in trunk are for NAV drive. The loose one is likely for other optional equipment and not used. The other little "box" is where two fiber optic cables connect.
I don't think it's related, but there are some ground wires running through the drivers side trunk hinge that go bad from flexing. Wouldn't hurt to check them.
Your convenience features warning typically is caused by the trunk battery failing or alternator. If you get a red message that would be your engine bay (aux) battery on the way out. The aux battery doesn't actually do anything but remain charged and waiting for emergency activation should the trunk battery fail and you need to use your electronically controlled brakes still. If the warning goes away after driving for a couple of miles you're alternators probably fine and its most likely that trunk battery needing a good charge or replacement. Best to trickle charge the battery to full.
Test you battery with voltmeter I'm sure you know it should be 12.4 or something.
To test the alternator you can bring a prompt up on the dash by triple tapping the odometer reset knob really quickly while the outside temp is displayed on the dash with the key in position 1 or 2 I can never remember. It'll show volts the car is receiving and when you turn it on it should be 13.5+ under load (AC, lights, music etc)
If you're struggling to bring up the volts on the dash search for the 'dyno mode' instructions, on the way to turning on dyno mode you'd it the volt display, so you can use the first couple of steps.
Often I turn my car on to find the battery conv warning (one every couple of moths), I suspect that sometimes when I remote lock the car it doesn't turn something off and gets drained. I drive it daily and it really does seem to be random when it crops up.. I have had all new batteries and alternator in the past year or so.
Your E55 looks like an early (but not the earliest) variant. Only one fuel pump relay with separate fuse in the trunk (now is the time to replace it with a 70-amp rated relay and socket). The earliest version had the fuse incorporated with the relay. The second relay that is "missing" is actually over the auxiliary battery in the engine compartment. Later variants moved the air pump relay into the trunk next to the fuel pump relay. The E55s built on or after 1 June 2005 have three relays in the trunk, one for the air pump and two for the fuel pumps. On the E63 they went away from relays and to the PWM fuel pump controllers.
04-06-2018, 10:53 PM
