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Various electrical gremlins 04 Cayenne S

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Hi All


I’m a new poster here but not new to Porches, actually this my 17th one!! I’d appreciate you help.


I bought an 04 Cayenne S with highish  mileage (125k) to carry my dogs in all weathers however it’s developed a series of electrical faults and I’m looking for guidance. Please bear with me on these, there are a few! 


Brake Proportioning Warning - this comes in randomly for a couple of seconds only when driving. There is a warning beep, another beep and it goes off again. I am aware of the water in the footwell issue and this has been checked out and it’s dry. I have also had the pcm unit reflashed by the main dealer and we also changed the brake pressure sensor (which was a pain!). It has been suggested that it could be a bad earth to the pcm/abs unit as the early cars used an unshielded earth, also suggested that it could be a corroded connector to the pcm unit. I stress that I don’t get the and warning or locked gears of the water ingress problem, only the random warning light. It happens during the day, at night, cruising along, stopped at lights. There seems to be no pattern. Help appreciated!!


Cruise control not working - the green light comes on but otherwise the stalk does nothing. I do have to press the brake to start so it’s not the brake pedal switch. No idea what the issue is! 


Rear wiper - has a life all it’s own! Sometimes it works perfectly, others it won’t stop and then stops in an incorrect place. The fact it does go on suggests it’s not the motor but really, I’m stumped with this one!


Central locking handles - the car opens without pressing the key button, provided it’s close to the door however the small black buttons on the handles do not lock it. It’s not fully keyless as you do need to put the key in and start it as normal, there is no start button or dummy key. None of the handle buttons work suggesting it’s not a failure of the handle itself as all 4 failing would be unlikely. Help!


its been well looked after and I’d like  to continue that. It may only be for the dogs but I’d like everything to work, anyway some of these could be the precursor to more serious issues that I’d prefer to nip in the bud. 


Final thing, we tested the battery and it seems fine. No issues at all however I’m aware that batteries can cause issues and so I’ll maybe change it regardless as a way of ensuring that it’s not responsible and for piece of mind.


thanks again all



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