P0rschegt2

Porsche 991 s PDK 2013. With key out of ignition, locked or unlocked, doors open or closed, the DME and fuel pump relays energise every 7 - 10 seconds. Left unattended the battery will go flat in no time, so dissconecting the battery for now . As soon as the key goes into the ignition it all stops. The car has no fault codes, it starts and drives with no isssues. If i drive the car, stop, get out and leave it, it takes about 30 minutes to start the process again. I see an old similar post from 2018 with no conclusion. Any ideas please?

asellus

how's the battery health? a dying battery will cause all sorts of odd electrical behaviour.

P0rschegt2

Fitted a new battery, same issues..

asellus

do you have entry+drive? if so, how far do you keep the fob from the car? I've never seen actual evidence of it, but there's the idea that having the fob within ten or so feet of the car will keep waking the car up. the fob doesn't broadcast though, so something would need to be continuously tripping one of the E+D sensors (door handle or frunk) with the fob in close enough range for a handshake to occur.

given the above hypothetical, my guess would be a door handle sensor is failing or has something near it with enough capacitance to trip it, but this is really grasping at straws. you could rule it out by disconnecting the door handle sensors, but that's not too trivial.

P0rschegt2

Hi thanks for your comprehensive reply. Does not have entry+drive, its a pretty basic car, not many options ;-) I have scanned the car on a number of occasions with my Icarsoft and no error codes, apart from the obvious with battery disconnection, terminal 30 on the gateway. The issue is similar to opening a door but every 7 seconds! The other thing i noticed is if I open the drivers door the dash lights up with the Carrera logo etc but when i open the passenger door the dash stays dark, possibly correct! They car is going in next Wednesday to an independant Porsche specialist I use, perhaps the diagnostics they use will shed some light. The Icarsoft is good, i can see and communicate with all the modules and all looks good.

vanlieremead

Sounds to me like an ignition key or relay failure. I have entry and drive. I just went to my vehicle and nothing happened as I approached it. When I lifted the drivers handle the door unlocked and some of the dash symbology annunciated (vehicle type, a light, a few other things not much more.). With the key in hand I turned on the ignition (I never remove the key turn unit) only to turn the car on and not to start. A whole bunch of other things happened including what I think was the fuel pump relay. Turned off and all went to sleep except for the lights which remained on for 30 seconds.

Try the same procedure. Does it work the same?

P0rschegt2

Yes, as I open the drivers door exactly the same as yours, the passenger door also does the same with the fuel pump but does not illuminate the dash. I have ruled out the door locks by removing the fuses to the door control modules. Place the key in the ignition, key not turned and the problem stops. I am working from US wiring diagrams, which were kindly posted on this site. Does anyone know where fuse box A, B, C, D etc are located? All I can find are the 2 in the front footwells and the fuse/relay pannel to the rear of the drivers seat behind the carpet where the DME relay is.

AlexAllPorsche

Hi,

I experience a similar issue on my 991.1
Any solution found yet on the issue of this very interesting post ?

have a lovely posche day !

WP0

Sounds like an electrical short due to mice, or bad relays…

AlexAllPorsche

thanks !
and do you have more info on the location of relays on a 991 ?

P0rschegt2

Hi, Investigating further, with an amp meter between the positive of the battery and the battery terminal, there is a 3.5 amp drain. This drain starts to fade after about 7 seconds and thats when the relays pulse again. The only way I have found to stop it, is to pull fuse Left footwell C 8 (PMS Control Unit). Even with this fuse pulled any electrical activity, even the luggage light or interior lights going of, will pulse the relays, just like opening a door. With left C 8 pulled the current drain goes down to 18 - 22 milli amps. The ignition module has been swapped out. Still no codes, car starts and drives no problem. I am still looking into!!!

WP0

Relays are in a few places: back of the car, under the luggage tray carpet, and under the driver side dash, depending on which relay is bad.