Help with high-pitch whine in cabin on new M4

[anthony_12347]

Just recently bought a new 2020 M4 Competition, and having one irritating issue that hopefully someone can help with.

Ever since around 1000Km, I started noticing a faint high-pitch whine in the cabin when the car was on. Didn't think too much of it, and tried to ignore it, but it's gotten significantly worse as the car has put on more mileage. It's to the point where anybody who rides in it comments on the noise, and it's becoming very irritating and worsening every week.

Here's some more details:
The noise sounds like a very distinct 'electrical' high-pitch whine or whistle. It is loud enough to be heard when windows are closed and can be heard over the stereo on low. It is continuous, does not change in pitch, and can be heard when stopped or moving. It appears to be coming from somewhere in the dash, or the engine compartment very close to the firewall. It does not change at all with the A/C or fan settings while the car is on or off. Saw some other forum posts where a similar noise was distinctly the A/C but doesn't seem like it here. I have also tried toggling interior, exterior lights, turning the display on/off, bluetooth on/off, makes no difference.

I also tried some different scenarios and here's what I found:
1. It's not the M4 seat logos. They do make a similar noise but they are off when driving.

2. When the ignition is turned on but engine is not started (press stop/start without foot on brake), it not there.

3. Once you start the engine, the noise can be heard. As soon as you take it out of park, even moving to Neutral, it gets even louder. After that, it's constant and does not very with RPM, Drive Mode, acceleration, etc.

4. Interestingly, using the Auto Stop/Start feature, when I come to a stop, the engine shuts off as expected while I'm in gear, but the whine noise is actually still present (and can be heard much more clearly), even after the car shuts the engine down.

So from what I can deduce so far, especially from the test from the auto Stop/Start engine shutdown, is that this seems to be coming from something electrical when the ignition is on, as I'm pretty sure the A/C and engine itself aren't at play here.

Going to give it a little while and then have the dealer take a look at it, but any advice to point me in the right direction would be greatly appreciated!

[mindspin311]

I have something similar in my 2018. It's not consistent, or at least I don't notice it being consistent. When I do hear it, it sounds like it's coming from the passenger side of the car. Feint like you said, even with the radio on.

[anthony_12347]

It started out very faint for me, I would only notice it if the car was very quiet, stereo off and windows closed. But it's definitely increased now to the point where I can hear it pretty consistently regardless of other factors.

It definitely gets drowned out by the exhaust in sport plus, but in Efficient mode, especially stopped at a light, it's very apparent.

I will try to take a video tonight to see if I can capture it to share.

Others have suggested ECU fan issue, exhaust valve actuator, etc..?

[jeffk182]

Any chance you disabled the active sound (fake engine noise) that's played through the speakers? I've read somewhere that after coding/disabling, some people had weird electrical noise through the speakers. Just a thought.

[Torfhinn]

On my 2015 the radio head unit fan was failing and causing a horrible squealing sound that would happen for just a few seconds after start up and randomly under heavy breaking on track days.

I took a video of this on my phone from several different days and brought that to the techs and it took them about 2-3 hours to find it and then 3 days to get the parts from Germany.

[mindspin311]

Originally Posted by jeffk182

Any chance you disabled the active sound (fake engine noise) that's played through the speakers? I've read somewhere that after coding/disabling, some people had weird electrical noise through the speakers. Just a thought.

I have disabled ASD. But cannot confirm whether thats when it started.

[turbo v6]

Had similar issue. The amp was replaced. Resolved.

[Beemerm3]

I think when u roll down the window u can hear it. Heard it might be you wheels. Needs some thing.

[anthony_12347]

So this issue spontaneously stopped. Don't hear the high-pitch whine anymore. Not sure if it was something loose or one of the fan's but seemed to have resolved itself.

Side note: Did disable the ASD but after this issue had stopped, so can't say whether or not it contributed to it.

[pbar]

Most likely the illuminated M seat emblem?

[sna66]

Originally Posted by pbar

Most likely the illuminated M seat emblem?

I'm pretty sure it's this, does it happen only at night and when you are in park or neutral? If so it's probably the lights

[Beemerm3]

Found out it's the cf mirror. Makes a high pitch noise. I decided to keep it since I can't remove the noise.