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Big noise like a bump on the speakers on the rear of my 996 4S (see no

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I have a 996 4S model 2004 with Bose Sound System + Dension Gateway for the iPod.

Everytime I unlock the car, I randomly ear a big bump coming from the back of the car. (similar to a bum coming from the rear speakers). This happening before I put the key on the ignition and turn on the engine.

One thing I noticed that the issue started after Porsche replaced the battery on my 996 4S but they are saing there is no relationship.

I already spent a lot of days trying to troubleshooting the issue without success and also the Porsche garage was not able to find the root cause.

In fact they told me to remove the Dension gateway but I don't think this issue come from the Dension Gateway. Yesterday I told them that I had a doubt with the amplifier that was replaced last year but they told me that I got the new version of amplifier so for them there is no relationship.

Does anybody in the forum experienced the same issue.

Many Thanks for your help.

Edited by liberatod
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  • Moderators

The last time i had this phenomenon, it was the amp, however there was no Dension present. To the content of your post, i have the impression that your dealer is not really willing to solve the problem, i would therefore choose another dealer.

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  • 8 months later...

The amplifier has been replaced 2x times by the local Porsche dealer but the issue is still the same and has not been fixed yet.


Basically, anytime I open the door of my 996 4S (specially in the morning time with very cold temperatures outside between -2 to +5 degrees Celsius) and sit inside the car, there is a big bump on the rear speakers. 


After 1 year troubleshooting this problem, I have the feeling that it is caused by the Bose amplifier itself with P/N: 996.645.333.07


I do remember that my 996 4S model October 2004 had a previous version of the Bose amplifier with P/N: 996.645.333.05 and it worked very well for years.


Anybody knows what is the difference between the following Bose Amplifiers listed below and how to escalade this issue to Porsche engineers?


  • 996.645.333.03
  • 996.645.333.05
  • 996.645.333.07


Best Regards,



Edited by liberatod
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  • 4 weeks later...

Hello All,

After 2 years troubleshooting and making multiple tests, I finally found the root cause of the problem and requested to get it escalated to Porsche AG in Germany.

In fact the amplifier was replaced 2 times with the last version with P/N: 996.645.333.07 but it generated always a random bump on the rear speakers after opening the door and sitting inside the car.


In some occasions there was no sound from the PCM or the sound come only from the front channels  ...


Be aware that this issue is happening in very cold operation condition close to +- 0 degree Celsius.


The workaround is to replace the amplifier with the version 996.645.333.05 which is the only workable model.


Loren, do you know if this issue can be escalated to Porsche North America in order to see if there is any evidence available?

In any case I think Bose should take their responsibilities and explain what is wrong on the amplifier 996.645.333.07


Best Regards,


Edited by liberatod
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