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Discussion Starter · #1 ·
I’m on a quest to sort out a long running issue with my partners 3.0 tdi. The battery keeps draining intermittently, like once a month. I’ve tried testing all fuses when the car is sleeping but no luck as it is intermittent. The alternator and battery test good. Pulled vcds codes and the only repeat ones refer to a non working speaker, headlight levelling related codes due to it being bought with a facelift light and bumper conversion, and now also a non working mmi (failed update by me🤦‍♂️). It is removed so not an issue just now. I’ve created a workaround using a battery brain, which cuts off the voltage when it drops low, and you switch it back on by remote or on the unit, so it can start before draining, but would prefer to fix it properly.
The main problem I can find is when the car is unlocked, I can hear the fuel pump primping every 20 seconds or so. It seems to stop when the door is opened? I am just wondering if this might be the issue as it shouldnt behave like that and she may forget to lock it sometimes and may be the fault.
I’ve tried researching as many possible ideas before posting, like trying to see if the ignition lock was dirty/not working, letting the pump issue run on and drain the battery. Also checked and swapped the fuel pump relay under the ecu, cleaned the ecu pins at the same time. It seems the signal to prime the pumps keeps working with the car off and doors closed but unlocked.
The car runs perfectly, no starting issues, I’ve been to a couple of local garages but I think I am more clued up than them, unless anyone knows a good vag garage on the east coast of scotland?
My only other thought is it could be a bad ecu? Any help on the pump or drain would be helpful.
 

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Blimey mate that is a good one!!! These cars are strong and well made for sure BUT they seem to be very sensitive to silly little electronic faults. PLEASE tell us a good VAG specialist!!!
 

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Discussion Starter · #4 ·
Got to the bottom of this a while ago myself by sheer luck, had the bum out of the drivers footwell, a pig to get to! Noticed some of the pins looked ever so slightly dirty/corroded so cleaned them up with contact cleaner as well as the connectors and board inside. Sorted it! Guessing a poor connection wasn’t letting it shut down properly once the key was removed, and keep on cycling like you had just inserted the key. Didn’t have an battery issues when it was left unlocked again. Might help someone else out, worth a try!
 
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