Polo 9N3: Central Electric System Draws 120mA Idle Current

Hello everyone,

As mentioned in the subject line:
My Polo is drawing 120mA of idle current through the central electronics control unit (fuse No. 40).

Does anyone know what might be causing this?

Best regards,
Volker.

Are there any entries in the error memory? After how long did you measure the quiescent current? What is the fault pattern you are observing?

Good evening, Stolley.


Are we talking about the Polo 9N 1.4 D, for which no one has yet performed an Autoscan? If it's about that specific model, I would suggest checking the current draw of your engine control unit (ECU).

In your case, I would examine the 3-pin connector on the left side of the fan housing. Please check the sw/ge wire for corrosion.

Since you've experienced issues with your vehicle related to the BNS (Battery Navigation System) before, the cause might be found there as well.

What exactly does the error look like, and is there an error scan available?


Best regards.

Michael.

vag-driver wrote:

Are there any entries in the error memory? After what time did you measure the quiescent current? What is the fault pattern you are seeing?

"There are no error codes stored in the system's memory. I measured the quiescent current approximately half an hour after removing the ignition key. The problem is that the starter battery was completely discharged after my 10-day vacation."

Ich_Can_nix wrote:

Good evening, Stolley, Let's talk about the Polo 9N 1.4 D, which is a model that no one here has seen before? If it's about this model, I would suggest checking the current draw of your engine control unit... In your case, I would examine the 3-pin connector on the left side of the fan housing. Please check the black/yellow wire for any signs of corrosion. Since you've experienced issues with your vehicle related to the BNS (Battery Navigation System) before, the cause might be found there as well. What exactly does the error look like, and is there an error scan available? Best regards. Michael

Hello Michael,

You probably mean a different Polo 9N3. Mine, with its mileage (548,000 km), tends to have mechanical problems more often...

I described the error message in my previous post...

But I can take a look at the plug.

When troubleshooting, please pay attention to cable breaks, chafing, rodent damage, or similar issues, as well as corrosion on the connectors.

Hi Volker,

Your introduction is very confusing to me.

stolley wrote:

My Polo draws 120mA of idle current through the control unit of the central electrical system (fuse No. 40).

I have now looked at a specific example, namely a 2008 Polo 9N3. In that case, the fuse SB40 does not connect to what is usually referred to as the central control unit, or body control module. Instead, fuse SB40 powers the engine control unit.

So, was exactly are we talking about here? Is it the engine control unit, or are we referring to a different fuse or something else?

If it's the MSG, the SB40 cable connects to pins 1 and 2 of the 121-pin connector. The wire color is black/yellow in the 2008 models.

If the control unit (MSG) continues to draw power, it's either defective or believes it still has something to do. For example, it might be running the cooling fan longer than necessary, or in some models, the water pump may continue to run. All of this should normally finish within a few minutes, and the idle current consumption should then decrease (provided that the corresponding sensors and actuators are functioning correctly). So, check with VCDS what the control unit reports in case of an error. In particular, see if any temperatures or other values are outside the normal range, which could prevent the MSG from going into sleep mode.

But please also include the MKB and MJ codes. It seems that in many configurations, the fan on the 9N3 is directly connected and not influenced by the engine control unit (MSG).

Regards,
Sure.

Here is the translation of the text from German to English:

"Guste" means "gust" in English. It refers to a sudden and strong gust of wind.

Thank you very much for your tips!

I'll probably have time to look into it more closely next weekend. I'll let you know as soon as I find out anything!

THANK YOU!