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350matt, Mechanical Engineer
Category: Porsche
Satisfied Customers: 23091
Experience:  BEng Hons, worked in the car industry for the last 22 years
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I have a porsche 991 (911). I have a new JL sub-woofer on

Customer Question

I have a porsche 991 (911). I have a new JL sub-woofer on the rear shelf and a lot of ECu modules underneath it shielded via the cars carpet etc. The e brake keeps failing and we cannot find faults and i am wondering if the magnets from the two subs are causing issues. The older cars had basically the same setup from factory and no issues? Any ideas as porsche doesnt know and i have a broken car still..
Submitted: 8 months ago.
Category: Porsche
Customer: replied 8 months ago.
Two faults are coming up - Ebrake inoperable and the stop/start is made inactive.
The brake module has been replaced by Porsche but the fault appears again and the brake locks on or off.
Expert:  350matt replied 8 months ago.


can I ask what happens if you remove the power to the sub-woofer

does this make any difference?

Customer: replied 8 months ago.
No we have tried that already. Also balanced rear brakes which is down is porsche computer as well. Also checked pasm system as well.
I drove the car 600 miles yesterday and the fault is now intermittent and comes up of its own accord. When the car is turned off it disappears and the reoccurs. Tried totally disconnecting the audio system to check for faults. Could the subwoofer be emitting magnetism into the faulty module or vibrations maybe?
Also porsche mentioned the brake actuators?
Thank you
Expert:  350matt replied 8 months ago.


its possible the addition of the sub-woofer magnet is upsetting the control module

you can make an effective magnectic shield by placing an aluminium sheet between the two

or even better there are specialised shielding materials like this

Customer: replied 8 months ago.
We have carpet, dynomatt, steel bulk head and an inch of high density foam before the modules, as well as a box crafted by JL audio with 40mm MDF and carpet covering. That's a huge amount of shielding in reality, I can't fit anymore without causing issues I don't think
Expert:  350matt replied 8 months ago.


EMF shielding is strange stuff as magnetic fields will pass through steel and organic materials very easily so while you have a lot of material there it will all be essentially invisible to the magnetic field

I'd suggest the next step is to remove the sub entirely and see how this effects things

Customer: replied 8 months ago.
Ok I'll try that. Also, porsche seem to think the battery is at 70% life and isn't perfect. It is an AGM unit and they think it maybe that causing the issue potentially. What do you think?
Expert:  350matt replied 8 months ago.


if the battery has been load tested and found to be wanting then this can create all sorts of issues as low battery voltage will give all sorts of issues

so its certainly possible