2009 Audi A4 2.0 battery drain

Ray Diagnostician North York, Ontario Posted   Latest   Edited  
Question
Electrical
Network Communications
2009 Audi A4 Quattro 2.0L (CAEB) 6-spd (0B2)
Battery Draw

The battery drain drops to near 0A when the Data Bus On Board Diagnostic Interface module is disconnected. I tried a used module but the drain is still there and then the customer needed the car back quickly, so I couldn't pull the codes. 

Does anyone know why that module is not going to sleep?

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Eri Technician
Larchmont, New York
Eri Default
 

A codescan might give u a clue on what’s draining the battery. but you should identify what data line is staying up hook up your scope to see who is not going to sleep

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Saifullah Diagnostician
Ottawa, Ontario
Saifullah Default
 

Probably not a comfy pillow. Data line can't sleep. Suggest counting sheeps

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Ray Diagnostician
North York, Ontario
Ray Default
 

Thanks Eri, I'll do that.

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Saifullah Diagnostician
Ottawa, Ontario
Saifullah Default
 

There is an input causing the module to stay active.

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Ray Diagnostician
North York, Ontario
Ray Default
 

Thanks, i'll scope the wires at the module to see which CAN wires are toggling

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Mario Diagnostician
Weston, Florida
Mario Default
   

First thing I'd do is check for codes, check for tsb, check module inputs

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Ray Diagnostician
North York, Ontario
Ray Default
 

Thanks Mario, I'll do that

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Dmitriy Analyst
Toronto, Ontario
Dmitriy Default
 

Hi Ray, along with what others said, here is one more consideration: while checking the codes look out for a CAN bus being in the one-wire mode. That Data bus module is a gateway for several CAN buses, some of them Low-Speed. The gateway will not go to sleep if an LS-CAN is in the one-wire mode. This can be caused by a wiring issue (for example, break in the door harness), or by one of the

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Ray Diagnostician
North York, Ontario
Ray Default
 

Wow Dmitriy, good info!

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Steven Mechanic
Spokane, Washington
Steven Default
 

The peaks of your scope pattern are 1.6 amps, but the valleys are 0.0 amps. The duty cycle of the pattern is approximately 50%, so you could guess that the average draw is about 0.8 amps. Also, you could try using the Measurement menu or a Math channel to get the average. At any rate, 0.8 amps is still too much. Have you found any documentation for how long you have to wait for the car to go to

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Ray Diagnostician
North York, Ontario
Ray Default
 

The amp ramps looks like the module is being turned on and off? I found one document that says to wait 2 hours for the modules to go to sleep. Thanks Steven

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Paul Owner/Technician
Los Angeles, California
Paul Default
 

Any evidence of water intrusion ....modules in the floor? Codes would helpful

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Ray Diagnostician
North York, Ontario
Ray Default
 

The car is in a body shop right now for some minor damage and when I get called back in to the shop, I'll ck codes in all modules.

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Ray Diagnostician
North York, Ontario
Ray Default
   

The first capture and the PSD file, is from the used Data Bus On Board Diagnostic Interface module J533 with the key off and the module should be sleeping. The module is slowly drawing from 0A to 1.5A, then the amps slowly go back down to 0A. The original module has the same slow on off current ramps. When the module turns on and off, the current draw should be a square wave. Any thoughts? The

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Chris Diagnostician
Commack, New York
Chris Default
 

All this is really good, but a complete vehicle scan need to be done before pulling the scope out. all the modules report to the gateway. we need to see if there are ANY codes. Dmitry is correct, if there are any codes for the data bus being in single wire mode, the vehicle may have issues going to sleep. Post the results of your code scan here.

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Ray Diagnostician
North York, Ontario
Ray Default
 

The car is in a body shop now, but when I get called in to diagnose the drain, I'll get the codes.

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