2006 M5 Battery Drain and No iDrive - ISTA Scanned, Ideas?

[xelif]

Bought a 2006 M5 in October. Don't think the seller was honest about the electrical issues...

Symtoms

• Battery drains after 2 days
• iDrive will not turn on. OEM screen will not turn on. I don't think its getting power.

What works:

• Radio, CD player, voice button all work.
• Fuses are good
• Installed and registered new AGM battery. The previous battery was the wrong type.
• I installed an aftermarket android screen which works but iDrive is still not accessible. I needed to use a different PEMP cable to the one on the car.
• Trying my best to find what the issue is. I am new to this.

This is closest I found online to what I'm experiencing:

Also found this today, going to check for water damage tomorrow:

ISTA Scan: https://drive.google.com/file/d/1zXC...vA3fKoXnl/view

Any guidance to help resolve this would be really helpful.
Located in Kitchener, Ontario, Canada

[aade]

Very helpful to supply the ISTA scan. The MOST stuff seems very broken and you might want to start by chasing this. That's all iDrive and that kind of stuff and it's fiber optic and likely won't work until you get the electric issues fixed.

To me this smells of wiring loom or some third party mod. Replacing the KGM as you wrote in your theory might be applicable, but it might also not be. Instead of opening up the parts cannon, try breaking out your multi meter and measure the connections from the fuse box to the DME as well as KGM.

Corroded lines or connectors (check for water ingress) from the KGM to the DME (PT-CAN is Power Train CAN) three wire bus: CAN-H, CAN-L and a wake-up) will likely cause cascading faults. Broken amp or TCU will cause the MOST link to fail, again it's fiber optic so no light, no life.

As for your battery drain issue, hunt down parasitic drain from third party mods. Spliced in speakers or whatever it might be. You can check this by seeing if there's a ground to ground current, it should be zero when the car is asleep.

The K-CAN (Karosserie CAN) controls things like lighting, air bags, steering angle (SZL), your iDrive and other stuff. Again, someone clamping on third party mods as simple as LED lights that aren't CAN compatible may cause this type of issue over time.

Here's what I'd do in order:

1. Baseline your power draw. Put a clamp around the positive lead (amp meter) and lock the car. Wait around 20 min and record the current.

2. Isolate MOST, by pulling the relevant fuse. I don't have the schematics for your car, but I think it might be F37 (TCU power). If the current drops, there's your power theif. If you have access to an ICOM A and an ICOM B cable, you can query the MOST bus separately.

3. Next is K-CAN, so unplug the KOMBI, CAS and KGM at one time (separate fuses, you'll have to look them up). Or, if you have access to a scope (I like Picoscope, but whatever will work) see if you're stuck low on the bus.

Once you get the car to sleep normally, go ahead and clear codes. Many of them are set by undervoltage and shouldn't return once you've chased down your apparent parasitic draw. You can wait with SMG, engine and airbag codes until you have your electrical situation fixed.

[xelif]

Ended up resolving this using a very good local shop. All in, cost about 1500 CAD.

1. New CCC fixed the idrive issues
2. Battery drain was related to a 3rd party tracker installed. It was hardwired into the main power. The lithium battery for the tracker was old and wasn’t holding charge so the tracker was draining the car battery.

[aade]

Glad to hear it worked out for you. Battery drain issues almost always end up being some sort of poorly installed mod.