KESSY Power Drain Fun and Games!

[Chrisrelfy]

Hi, I am new to writing posts in forums so be gentle…. I will try to add as much relevant information as I can.

 

Firstly I would like to thank some of the other forum members who have helped me so far to try and diagnose the problem I am currently having.

I amongst others I have read:

https://rennlist.com/forums/cayenne-955-957-2003-2010/1056770-kessy-unit-drain-my-battery.html

https://www.renntech.org/forums/topic/37055-keyless-kessy-entry-problem-fixed-after-5-dollars-and-1-hour-o/

 

Although these posts have helped me to narrow down what the issue I am having might be, they haven’t solved the power drain problem I am having.

My troubles started a few months ago after buying a 2003 Porsche Cayenne Turbo 955. The car is low mileage for its age (74k) but is suffers from a flat battery after standing for roughly 2 days. The previous owner used to keep the car on a constant trickle charger stating “These old cars all have flat batteries after 1-2 days”. I knew that isn’t true but as someone with previous experience with parasitic power drain issues with cars I didn’t get too worried about the problem.

 

The battery on the car is new (bought by the previous owner, it’s the correct size and I have a receipt to prove its age!).

 

Things I have done so far:

·         Used a battery tester to fully verify the battery is good.

·         Pulled fuses to confirm which fuse was the culprit. I did this after connecting an analogue ammeter between the battery and the car. After waiting for the initial current spike to calm down I found that Fuse 41 (KESSY) on the left hand side fuse panel was causing a 2 amp draw. After removing the fuse the current draw dropped to almost nothing (that I could read using the analogue readout).

·         After finding out that Fuse 41 was the culprit I removed the fuse and wired in a remote control relay as a temporary fix to stop the power going down when the car is not in use.

o   This “bodge” solved the power drain problem, however it’s not fixed the original issue, it’s just a sticking plaster!

o   After reading another post it was mentioned that the KESSY transmitters/receivers which are in the doors and the bumper can cause a parasitic power drain where that’s a faulty unit. I have since removed all of the KESSY units from the car and…. No luck.

o   I had a quick look today to see about replacing the KESSY ECU itself but it looks like a pig to get to (it’s above the driver side foot well) there is a thick as your arm wiring loom coming from the bulkhead going right underneath where you could remove it. So I am not keen on replacing… also a call to a Porsche main dealer mentioned that they have only sold a handful of replacement KESSY ECUs so they suggested that’s unlikely to be fix the issue, however I'm not sure.

 

I am now completely out of ideas.

 

Anyone else had a similar problem(s) who could offer some advise?

 

Thanks very much in advance,

 

Chris.

[Chris Farmer]

I read the gist of your other threads, sounds like you rather enjoy chasing demons.  So you traced it to the fuse which is good but I assume that node is connected to a number of loads?  Have you tried chasing the drain to it's final destination?  Rather than passing the current through a 4 port meter you can use an AC/DC clamp meter.  I have this cheapy and it works well enough for a 2 amp reading.  If you trace it completely you can rule out faulty wiring and focus on PCB faults or programatic issues.  

 

Programmatically I assume there is a low power mode for most/all of the controllers in this vehicle that are permanently connected to 12v.  This is likely transmitted over CAN bus but might be a hard line.  Find out how the module is put to sleep and verify the correct messages/signals are being sent.  If they are... then you have narrowed the problem down to parasitic losses on the PCB.  In my experience  short circuits like this on a PCB (2a at 12v) would be rather obvious visually or thermally.  It's alot of power to be dissipating on a PCB through a failure so if you don't see burned parts or feel hot transistors/resistors then it's most likely just operating normally; just not in a low power state.

 

I'll be getting a Porsche SIT manual soon (it sin the mail) but it's for the 2004.  Hopefully it has some info on the KESSY system.  I am interested in this issue because I also have some battery drain issues, though not nearly as severe and I haven't bothered tracing it out yet.

 

 

Edited January 30, 2019 by Chris Farmer

[John shearn]

I have same issue but today I have the dreaded “ steering faulty “ red sign up !!!!!

not sure best course of action !