GMIII/P-Bus 16minute sleep. How to tap power? Genuine advice needed.

[HoZy]

Hi all,

I have a USB wifi module in my E39 I use with my headunit, I hate waiting for the WIFI to boot every time I start the vehicle etc.

Long story short I'd like to tap power from a module or somewhere in my system to either use in conjunction with a relay or just with a 12v-5v step down for the USB WIFI.

This means it'd stay on for 16minutes, or Power up as soon as I unlock the vehicle after an extended period of time.

I would also like to use this power source for a new dash cam for that 16minute timer etc.

I am referring to this system.







Cheers
Mat

[edjack]

The cigar lighter stays on, at least on my car. Get a USB power adapter.

[HoZy]

The cigar lighter stays on, at least on my car. Get a USB power adapter.

Not the case here unfortunately.

Cheers
Mat

[Mike WW]

All I can say is be careful, that sleep mode is a funny thing. When I was having radio problems with it cutting out, on rare occasion it would prevent sleep mode from occurring, leading to a dead battery in the AM, due to the radio not working. Monitor it a few times after install, the A/T position indicator goes off when it goes to sleep.

[geargrinder]

Yeah the cigarette lighter wouldn't help anyway as it'd be perma-hot and would kill the battery over long-park times.
OP wants it to go to sleep, just wants it to wake up at door-open so it's booting as he's getting his buttocks situated.
I like the theory by the way... my custom audio system amps are now turn-on from the factory amp turn-on signal, but maybe I should look into this as well. The amps have varying levels of slower turn on so if I'm leaping in real quick, when I start the car I get a few secs of silence then the rears kick in first then finally the fronts come on. Would be nice if the amps were pre-booted when the headunit comes on.

Anyway: Hit the wiring diagrams (known as the "WDS" in BMW-speak) on bmw-planet.net
Yes you have to fork with your browser config and possibly browser choice (I use older versions of Firefox, seems the easiest route to getting it working), but yes it will work and will have all the answers you seek. You def can tap into the switched sleep power, just prob take some time to find a combo of a 'good place' and a 'convenient place'.

Mike - I don't think this situation will keep the car from sleeping. The radio is different because the radio can send bus signals to the GM to indicate "hey something is alive and doing things", whereas his wifi unit will be 'invisible' to the GM and the GM will happily cut power to it after the time expires.

@Hozy - post back w/ what you find/decide on this, as might be helpful to me if I decide to mess w/ this...

[Mike WW]

Mike - I don't think this situation will keep the car from sleeping. The radio is different because the radio can send bus signals to the GM to indicate "hey something is alive and doing things", whereas his wifi unit will be 'invisible' to the GM and the GM will happily cut power to it after the time expires.

Could very well be, I just meant it as a caution given my difficulty in trying to decipher the buss system, how it works and why.

[HoZy]

Okay, I'm back home after my time away and I'll hopefully be tackling this soon.

Just putting this link here for reference so I don't lose it.

GMIII Pinouts: https://www.bmwgm5.com/GM3_Connections.htm

e38/e39 bus system: http://e38.org/bussystem.pdf

random info: http://www.bimmerfest.com/forums/sho...5&postcount=21

note: check fuse 24 & 38 for power with ignition off & after 16minutes. Power for shift gate illumination on automatic.

Cheers
Mat

[HoZy]

And after some tinkering & WDS reading I think we have what we are after.

Snipped this from the WDS





Cheers
Mat

[geargrinder]

Mat - Since I've been curious about this... I looked at the WDS...

Looks to me like there's 2 ways that could be pursued.

The GM switches Pin 19 on connector X254 on/off to relay K72 on/off for seat /steering related functions (because those are big motors it needs a relay so the heavy current isn't going through the GM). Basically the best way to do that is to use the output of Fuse 13, and no the GM driver. For anything drawing some power this would be the best route.

http://www.bmw-planet.net/diagrams/r...000010333.svgz

Whats interesting about that is that the relay gets switched on/off by the ZKE on the 16min delay, but it also seems switched by the ig switch, which looks like an 'override' circuit, i.e. if the ZKE is malfunctioning for some reason and hasnt switched on K72, the K72 relay will be switched on by ignition directly when its turned on.

The GM also switches Pin 20 on connector X254 on/off for all interior lights, as you show above (same pin goes to all other interior lights). This might be OK for something really light duty but I kind of like using the F13 out of the other relay better.

[MN2K740i]

Where are you looking to install this module? I have a perfect wire to tap if you have a DSP amp in the trunk. It's how I tapped in the power for my DSP adapter in both my cars for my GROM Bluetooth unit. Car goes to sleep, my GROM breaks the connection, I unlock or open the door, it powers up and is connected to my phone and music plays before I even start it. Set it up that way because I didn't want that lag time of dead air when I start the car waiting for my Bluetooth to connect and everything...It's just like a regular radio pretty much now. Car starts and plays once the audio system initializes.

[geargrinder]

HoZer did you ever sort this out?

- - - Updated - - -

Where are you looking to install this module? I have a perfect wire to tap if you have a DSP amp in the trunk.

Is it the standard DSP turn-on white wire? Because that doesn't come on until ignition is switched on. Would be interested in what color/wire you were using if not... I'd love to pre-load my amps & aftermarket DSP as I'm putting my old boney ass in the seat getting ready to take off...

[HoZy]

HoZer did you ever sort this out?

I've been side tracked with so many other things but I did end up tracing how I'd do it, positive from the glovebox light as a trigger for a relay with constant grabbed from the fuse panel.

Did all my tests with multi meter & waiting 16 minutes between all tests. I'll be using a 12v to dual 5v 3a usb adapter from eBay, powering a dash cam & the usb wifi modem for my stereo.

Depending on weather I'll actually do this most likely next weekend since my heater core should be here.

Cheers
Mat

[geargrinder]

Cool. I want a connection in the trunk area and am real tired of running wires under the center console and rear carpet, so maybe I'll hope MN2KXYZ replies w/ something back there... But I could also take your idea and tap to any of the lighting I believe. I dont' need current, just voltage (all audio stuff has supply power, I just want the sleep-turn-on...)

[HoZy]

Cool. I want a connection in the trunk area and am real tired of running wires under the center console and rear carpet, so maybe I'll hope MN2KXYZ replies w/ something back there... But I could also take your idea and tap to any of the lighting I believe. I dont' need current, just voltage (all audio stuff has supply power, I just want the sleep-turn-on...)

Luggage compartment lighting I assume means trunk if so the trunk light circuit is energized for those 16 minutes, however if the trunk is open it'll ground the globe causing it to illuminate.

Remove the trunk bulb, throw a multi meter on it. leave the car unlocked for 16 minutes & confirm it turns off. Then open a door or unlock the vehicle via remote. You can also simulate the trunk being shut by using a screwdriver to lock the mechanism, Just remember to unlock it and not slam it down.

ASK ME HOW I KNOW! Did it while using a battery minder a few years ago and had to align the latch again.

Cheers
Mat

edit: Personally if that method works I'd still use a relay since the battery is in the trunk & there are a lot of spare relay spots at least in my E39. Just don't forget to fuse it.

edit2: Just thinking, Do E39 lights dim or turn off when cranking/starting? I don't remember off the top of my head.