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outrun
Newbie


Joined: 25 Jan 2019
Posts: 4



PostPosted: Fri Jan 25, 2019 9:46 am    Post subject: 2004 Cayenne S Brake Portioning fault HELP! Reply with quote

Hey

I have an 04 Cayenne S (955) which is showing an odd fault. Please can anyone help?

The car drives fine, however I sporadically get a Brake Portioning warning come up in the centre display. It comes up and goes off in 2 or 3 seconds and have no noticeable affect on the way the car is driving. The fault happens in several situations so I haven't been able to find any pattern to it - happens when waiting in traffic, when driving, it doesn't seem to be when I press the brake so I don't think it's the message to the abs unit to apply the rear brake lights.

There is a fault which is common that brings this warning up, along with abs warnings and sometimes locks the car in gear that is related to water ingress into the wiring harness under the passenger (rhd) carpet. It is not this, we have checked and there is no water in there and the drains are all clear.

The main dealer reset the PSM unit and no faults where found as well.

Logically, there is a momentary miscommunication in the system which makes the car think there is a brake balance issue however, I don't think there is an actual issue. Trouble is, with no fault codes stored. we can't work out what the problem is!!

Any ideas or experience on this would be most welcome. Where the fault doesn't affect the drive, it could be the precursor to something more serious and so I've like to trace it down.

Cheers in advance!
 
  
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HSC911
Long Beach


Joined: 23 Jul 2014
Posts: 6748
Location: Bedford


PostPosted: Fri Jan 25, 2019 5:31 pm    Post subject: Reply with quote

Welcome

DeMort will be along later, he will answer this Thumb

Had any other Pork Dont know

Say hi bye in the Newbie section whilst you're waiting thumbsup
 
  
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outrun
Newbie


Joined: 25 Jan 2019
Posts: 4



PostPosted: Fri Jan 25, 2019 9:42 pm    Post subject: Reply with quote

HSC911 wrote:
Welcome

DeMort will be along later, he will answer this Thumb

Had any other Pork Dont know

Say hi bye in the Newbie section whilst you're waiting thumbsup


Not really a newbie, just couldn’t remember my old login as I’ve not visited for a few years.

I’ve had many Porsches....

2 x 993tt
2 x 996tt
1 x 993c4
1 x 996c4s
1 x 996c2
1 x 964c4
1 x 928gts
2x 928s4
1 x 968tip
2 x 944

And if all began in 1995 with a mint condition 924!

I moved to Italian stuff in the past years but have the big cayenne for my dogs as I can't entirely escape from Porsche !!!
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7584
Location: Brighton


PostPosted: Fri Jan 25, 2019 9:42 pm    Post subject: Reply with quote

There are 2 faults this might be related to ..

1 / there is a vacuum pump o/s/f wing .. the pipe is prone to cracking .. this will flag a fault .

2 / water can get into the PSM unit via a poor wiring connection .. an earth on the o/s/f bulkhead .

I would lean towards no. 1 but this is a garge check im afraid , its not what i would consider a diy fix .
_________________
.
My Daughter's Crowdfunding has hit the target .

Thank you all so Very much .

She's not going until july 2020 though .



Mechanic

7pm - 9pm

Now At An Indy.
 
  
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HSC911
Long Beach


Joined: 23 Jul 2014
Posts: 6748
Location: Bedford


PostPosted: Fri Jan 25, 2019 11:51 pm    Post subject: Reply with quote

outrun wrote:
Not really a newbie, just couldn’t remember my old login as I’ve not visited for a few years.

I’ve had many Porsches....

2 x 993tt
2 x 996tt
1 x 993c4
1 x 996c4s
1 x 996c2
1 x 964c4
1 x 928gts
2x 928s4
1 x 968tip
2 x 944

And if all began in 1995 with a mint condition 924!

I moved to Italian stuff in the past years but have the big cayenne for my dogs as I can't entirely escape from Porsche !!!


Guess you've got a sh!t memory then Grin



Thumb
 
  
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outrun
Newbie


Joined: 25 Jan 2019
Posts: 4



PostPosted: Sat Jan 26, 2019 6:37 am    Post subject: Reply with quote

HSC911 wrote:
outrun wrote:
Not really a newbie, just couldn’t remember my old login as I’ve not visited for a few years.

I’ve had many Porsches....

2 x 993tt
2 x 996tt
1 x 993c4
1 x 996c4s
1 x 996c2
1 x 964c4
1 x 928gts
2x 928s4
1 x 968tip
2 x 944

And if all began in 1995 with a mint condition 924!

I moved to Italian stuff in the past years but have the big cayenne for my dogs as I can't entirely escape from Porsche !!!


Guess you've got a sh!t memory then Grin



Thumb


Yes indeed. Could be age but it’s probaby whisky.
 
  
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outrun
Newbie


Joined: 25 Jan 2019
Posts: 4



PostPosted: Sat Jan 26, 2019 6:39 am    Post subject: Reply with quote

deMort wrote:
There are 2 faults this might be related to ..

1 / there is a vacuum pump o/s/f wing .. the pipe is prone to cracking .. this will flag a fault .

2 / water can get into the PSM unit via a poor wiring connection .. an earth on the o/s/f bulkhead .

I would lean towards no. 1 but this is a garge check im afraid , its not what i would consider a diy fix .


Cool, cheers, I will have this looked into. It’s not the Psm unit, that’s been checked and software update by the main stealer.
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7584
Location: Brighton


PostPosted: Sat Jan 26, 2019 7:10 pm    Post subject: Reply with quote

I would suggest useing an Indy over an OPC for this .. its unlikely most OPC guys have worked on the Cayennes very much and there is no training from Porsche for them .

I did over 10 years at an OPC .. i know how the guys are trained and there is nothing on any car thats not current so if you joined an opc 5 years ago you will have no training on these .

They may well say the PSM is ok .. they do suffer from water ingress for 2 reasons .. not only the range of cars that had no sheilding on the earth wires but also due to dirt build up over the same wires.

The only true check is to remove the the psm plug .. it can be done but is a bit of a mission then actually look inside for corrosion .

Ive seen about 10 of this type of fault over the years .

Basically there are three main faults with this system .. the 2 i have mentioned and the brake pressure sensor under the master cyl filling with dirt and giving a false reading .. you WILL get a fault code for this though and its specific to this item so im of the opinion its not this .


These are the usual faults anyways and theres nothing to say this is whats wrong with yours .. but its probably what i would be looking at first .
_________________
.
My Daughter's Crowdfunding has hit the target .

Thank you all so Very much .

She's not going until july 2020 though .



Mechanic

7pm - 9pm

Now At An Indy.
 
  
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