Fuel level sensors/senders- why two and which is which? 2010 S5 4.2

[JK01.4.2A6]

My gauge and miles-to-empty aren't working. Based on other posts, it sounds like a fuel level sensor, but there are two. Why two? And which is used by the gauges? Thanks!

[JamesRS5]

Isn't one for the gauge and one for low level warning?

[JK01.4.2A6]

Hmmmm. Maybe. But when mine works from time to time, the fuel level warning goes out, the gauge reads a credible level, and the miles to empty reads a number that seems right given the gauge reading, so I suspect that all three activities are driven from one sender.

Since I posted this, I've read that there are two senders because the tank has to bend around over the Quattro drive, which means it has two low points. The second sender activates a second fuel pump which pumps fuel over to the other side to maintain the same level in each side. Can anyone verify this? And which sender is which?

Thanks for your thoughts.
Jim

[JK01.4.2A6]

OK. I fixed it. First, I diagnosed a defective Fuel Sensor 2 (G169). Though I suspected it from the symptoms, I confirmed it when I traded in my old Ross-Tech cable (left over from my 2001 A6) for a new cable, and read the codes. So I was getting ready to replace it, and even had a shopping cart loaded at ecstuning.com with the parts, when I thought I'd check the resistances as a final confirmation. I pulled the back seat cushion, and took off the access panel over the fuel pump and Sensor 1, and immediately saw my problem. See photos....

A mouse had moved in for the winter and built a nest. When I vacuumed the nest materials off, I found that the wires going to the two pin electrical connector were chewed through and touching. I removed the contacts from the connector shell, stripped the wires back, soldered them on, and reassembled. Everything's working again.

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