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Audi0405, Technician
Category: Audi
Satisfied Customers: 10670
Experience:  10 years in Vw and Audi Field
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Actually it's a friends Audi, it's a 2005 A6 (C6) 4F2 with a

Customer Question

Actually it's a friends Audi, it's a 2005 A6 (C6) 4F2 with a 130KW BDW engine. After some time being parked 6-8hrs most of the time. At some moment the lights on the dash come on EPC, ESP, ABS, (!) and airbag light while the car is still locked. It that state remote does not react. When opened with a key, if the key is inserted into the steering wheel lock it gets trapped there. When measuring the voltage on the poles under the hood the voltage is about 3V. With a small booster or helper battery the car comes to life and gives free the key or enables easy start. At the moment of connection outside battery the light on the dash extinguish, the key can be removed, or the car started. During the subsequent diagnosis can be observed that something was draining the battery until the battery came to the lowest power restriction level. The battery is new properly coded Exide battery, the generator is fully functional. I am considering a problem in instrument cluster or the energy management module which separates the battery minus from chassis, but I do not know how to conclusively diagnose either one of them or neither of them. Can you assist?
JA: Has the light been on for some time? The Audi Mechanic's require payment for their services. It's way less expensive on JustAnswer than face-to-face would cost. Are you fixing your A6 yourself? What have you tried so far?
Customer: Yes, we are trying to do it our-self. The battery has been changed and properly coded. The generator has been removed, tested on the testing table and put back. The logs from the energy management unit show continuous current discharge of about 2-3Amps. At some point the dash lights the mentioned lamps. I do not have any clue how to decide diagnose a specific component. The suspects may be the dash insert (j285), the energy distribution box (j519), central convinience (j393), the battery manager (J644). On older cars I would have pulled the fuses one by one until I found the circuit that causes the drain, but on such a car there must be a better way, even when the diagnosis does not give a clue.
JA: Anything else you want the mechanic to know before I connect you?
Customer: No, I think I have written all of it
Submitted: 6 months ago.
Category: Audi
Expert:  Audi0405 replied 6 months ago.

The best way is the way you have described where you remove the fuses one by one and see which system is causing a draw the most common issue on these vehicles to cause a big draw like the one you are having is the body control module just like the energy management module but you will need to put a amp meter and star puling fuses the way you will know for sure where the issue is coming from .

I hope this helps please dont forget to provide positive feedback for the help provided thank you