Exhaust Gas Recirculation (EGR) Potentiometer: Low Signal When Hot

Hi,
I have an Audi A6 4F with a 2.0 BRE engine that's experiencing a problem.
"When the engine gets too hot, the glow plug warning light comes on, and this is stored in the error memory."
001031 - Potentiometer for exhaust gas recirculation (G212).
P0407 - 000 - Signal too low - Intermittent.
Freeze Frame.
Error status: 00100000
Error priority: 1.
Error frequency: 1.
Mileage: 214,000 km
Time: 0.
Date: 2015.05.08
Time: 18:09:40

Freeze Frame.
Speed: 2037 /min
Speed: 110.0 km/h
Last: 40.8%
Lambda: -4.9%
Air mass/flow rate: 1050.0 mg/H.
Air mass/dose: 1005.0 mg/H
Binary value: 00000000

Sometimes, but very rarely, something else happens as well:
01027 - Exhaust gas recirculation (EGR) valve (N18).
P0403 - 000 - Malfunction - Intermittent.
Freeze Frame.
Error status: 00100000
Error priority: 1.
Error frequency: 2.
Mileage: 213,998 km
Time: 0.
Date: 2015.05.08
Time: 18:07:17

Freeze Frame.
Speed: 882 RPM
Speed: 0.0 km/h
Key press ratio: 84.4%
Voltage: 13.68 V
Air mass/Hub: 480.0 mg/H
Key press ratio: 0.0%
Binary value: 00000000

It started happening after I replaced the EGR valve. However, it wasn't the EGR valve that was defective; it was a different issue – the teeth on a gear had broken off.

Now it's unclear whether the new AGR (Abgasrückführung - exhaust gas recirculation) system is also defective, or if the problem lies elsewhere.
Where is the potentiometer for the exhaust gas recirculation (EGR) system located? Is it built into the EGR valve itself, or somewhere else?

And another question: I have a used AGR valve here. I tried to verschandeln it and noticed that you can rotate the flap without the shaft turning. Is this intentional, or is this part also defective?

Thank you very much for your tips. I already asked on Motor-Talk, but I haven't received any answers yet.

PS: Sorry for my bad German, but I think it's somewhat understandable what I described .

Quote:

Now it is unclear whether the new EGR valve is also defective, or if the problem lies elsewhere? Where is the potentiometer for exhaust gas recirculation located? Is it inside the EGR valve itself, or somewhere else?

It looks like there's a defect... or a broken cable.

Was the replacement part an original part, or possibly cheap, low-quality junk from East Asia?

I'm not entirely sure, but I think it's a replica; I bought it on eBay, and this is the part http://www.ebay.de/itm/151554678441?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT.
"The other valve is definitely original, but I'm not sure now if it's supposed to have that flap."

Quote:

The other valve is definitely original, but I'm not sure now if it's supposed to have that flap.

A loose flap that just flutters back and forth is non-functional. It's best to compare it to the original part.

I think there's a high chance that the item purchased from the online marketplace is defective.

Unfortunately, I no longer have the original part I foolishly threw away too quickly.
Wo ist denn eigentlich das Poti dafür eingebaut? Inside the valve itself?
Looking at this, it seems like the valve is controlled from an external source.

Unfortunately, it's not working, and I have no idea why. It's an MP4 file and it's 40 MB in size, which should be fine, but it's not working.
It's not really interesting, as you can only see that you can rotate the flap on the axis by about 15 degrees without the axis itself rotating. And I don't know if that's supposed to be the case or not.
Edit: It actually worked, but the video was cropped, so it's even harder to see now.

"Works perfectly, thank you very much!"

Quote:

And I don't know if that's supposed to be like that or not.

No, I would re-weld it in the correct position. The resting position is: closed.

Quote:

Where exactly is the potentiometer installed? Is it inside the valve itself?

Yes. It's possible that it also has an inductive sensor installed. If you bought that part as shown in the video, it's quite likely to be defective.

Okay, thank you very much for the tips. I will let you know when I have made more progress.

Hello,

I just got back from the workshop, and I installed a new, genuine AGR valve this time.
Drove 40 km on the highway, and the warning light came on again, and errors were stored again.
Potentiometer for exhaust gas recirculation, signal too low.
What's your next suggestion for something I should check?

Quote:

Do you have any suggestions on what I should check next?

Definitely include the wiring harness with the connector for the AGR (Abgasrückführung - Exhaust Gas Recirculation).

Best regards, Rainer.

Yes, as far as I could, I inspected the wiring harness (visually) and didn't find any damage.
The day before it started, I drove over a traffic island at night, quite roughly, and it made a loud noise. The next day, the warning light came on. Could it be related?

Nachtrag! Habe gerade nochmal geguckt, vielleicht lag es dieses Mal am Stecker, der war nicht richtig drauf glaube ich. Dabei habe ich gemerkt wenn Motor aus ist und Zündung an summt irgendwas unter der Motorhaube ich glaube das ist der AGR selbst, ziehe ich den AGR Stecker ab, hört Summen auf. Wenn ich Zündung aus mache summt es noch 2-3 Sekunden macht Klack-Klack und dann ist Ruhe. IsIs that normal?

And the plug doesn't click into place properly anymore; that small latch that secures it has broken off. Is there perhaps a trick to getting it to stay in?

Quote:

And the plug doesn't click in properly anymore; this small latch that locks it in place has broken off. Is there perhaps a trick to get it to stay in?

It's best to replace it if the plug is available for individual purchase.

Otherwise, one or more cable ties might help you temporarily secure the plug.

You should definitely take a close look at all the connections, from the AGR to the STG.
Perhaps there are increased contact resistances somewhere in the chain or within the control unit (ECU) itself, especially when the vehicle is hot.

Okay, I'll try that out this afternoon. I'll let you know how it goes.

So it goes! I reinstalled the plug and that was it. Now it clicks in properly and there are no errors. I just drove 280km without any error messages!
Thank you for your tips and help.

Great .