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  • 3 weeks later...

It happened again.

Got the brake code:

P1431

Brake Booster System - Signal Implausible

(The brake system is working just fine at the same time)

Got another code in electrical system simultaneously:

Fault code 0907

Load management operation on vehicle electrical system/

DME control module

Possible causes of fault

♦ 'no display' Loads are/were switched off temporarily. The load

management operation was enabled because of undervoltage.

Also noticed that this usually happens when the car has a few back to back short trips in one day.

All these above makes me wonder if I need to get a new battery for my cayenne (80k on the clock)...

Edited by TopGun2000
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0937 fault is a garbage fault, thats probably in every Cayenne out on the road. As for your brake booster faulty warning that is a real fault and will need to be diagnosed. An old battery will cause some random faults in these cars but I've never seen it throw one of these. A few things to check before spending any money... Check the operation of the electrical vacuum pump and see if you have any vacuum leaks in the lines running to the booster.

Edited by PTEC
  • Upvote 1
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It happened again.

Got the brake code:

P1431

Brake Booster System - Signal Implausible

(The brake system is working just fine at the same time)

Got another code in electrical system simultaneously:

Fault code 0907

Load management operation on vehicle electrical system/

DME control module

Possible causes of fault

♦ 'no display' Loads are/were switched off temporarily. The load

management operation was enabled because of undervoltage.

Also noticed that this usually happens when the car has a few back to back short trips in one day.

All these above makes me wonder if I need to get a new battery for my cayenne (80k on the clock)...

Possible fault cause (P1431)

♦ Leaks in brake booster system

♦ Vacuum pump worn out or mechanically faulty

♦ DME control module faulty

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it happened again today. :(

do i need some special tools to check the vacuum pump and hoses?

Yes, you do. You need a special tester that can build up the vacuum to -400 to -600mbar in the brakebooster and then let it stay there. After a while you will read out the values and see if it is the same vacuum.

To check if the vacuum pump is OK you will need a Porsche system test II. It will do the adaptations och se if it is OK.

Take the car to a Porsche workshop =)

  • Upvote 1
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I had the same problem with my '04 Turbo. It turned out to be a broken vacuum hose on the passenger side, underneath the plastic cover, next to the windshield fluid filler tube. Start the car and listen for vacuum suction noises. The Porsche dealer said its a very common problem at that location cuz of the heat from the turbo.

Also the code was still there after I replaced the hoses and when I took it to them they said when the hose broke it sucked a bunch of dirt in the vacumm pump. They blew out the pump and everything is fine now.

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I had the same problem with my '04 Turbo. It turned out to be a broken vacuum hose on the passenger side, underneath the plastic cover, next to the windshield fluid filler tube. Start the car and listen for vacuum suction noises. The Porsche dealer said its a very common problem at that location cuz of the heat from the turbo.

Also the code was still there after I replaced the hoses and when I took it to them they said when the hose broke it sucked a bunch of dirt in the vacumm pump. They blew out the pump and everything is fine now.

I really appreciated your input. I will definitely look into that. :thankyou:

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  • 2 months later...

04 TT, same fault, "brake booster warning".

Same problem as TopGun2000. the hose/plastic pipe is cracked at the connection (bottom end). Most likely due to heat exposure. Wrapped electrical tape (for now), i guess 3/4" heatshrink will also do.

P/N is 7L5-611-931 G. Cleared code, seems ok.

it is under pass side engine cover (remove blue washer lid, remove torx screw at lid, loosen rubber gasket around, remove that "+" screw lock thingy, remove plastic cover, and it's right under the plastic cover.)

15 minute job total.

Thank you Renntech, thank you Durametric!

I found the problem: a cracked vacuum line (on the top of the hose at the "931" mark)!!! :cheers:

post-40916-126669642814_thumb.jpg

Obviously there was another old leak which was fixed by the previous owner in a JB Weld way. :jump:

post-40916-12666962851_thumb.jpg

:renntech:

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  • 4 months later...

I found the problem: a cracked vacuum line (on the top of the hose at the "931" mark)!!! :cheers:

post-40916-126669642814_thumb.jpg

Obviously there was another old leak which was fixed by the previous owner in a JB Weld way. :jump:

post-40916-12666962851_thumb.jpg

:renntech:

The part number for the lower hose is 955-355-577-51 (thanks to Luke at Sunset). The other part number quoted by Spyrwebs is for the upper hose that number 931 is visible on the top.

I have a question: Once the hoses are replaced, does the warning displayed in the instrument panel go away or do I need the Durmetric tool?

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  • 1 month later...
  • 4 weeks later...

I fixed mine by cutting off the broken hose below the one-way valve down to just above the 90o bend. I used some 1/2 inch vaccum hose to slip over the remaining pipe and bend.

Then I clamped it with a hose clamp, and clamped the other end to the bottom of the one way valve and re-inserted the one-way valve into the top part of the pipe.

Total cost about $10 and 30 minutes time, plus the new hose is so thick it'll never crack again.

Error message went after two starts and a bit of a drive.

Cheers!

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