Linear Lambda Sensor: What You Need to Know

Hi,

Can someone explain to me what a "linear probe" is? I have two probes installed in my BGU engine (in an Audi A3), one before the catalytic converter and one after it.
Does the term "linear probe" refer to both probes in general, or only to one of them?

It's showing me two error codes:

17 589 Linear lambda sensor - Warning light ON.

and

Bank 1, Sensor 1.


What is meant by that: before "KAT" or after "KAT"?

Linear lasers are broadband probes consisting of a measurement cell and a pumping cell.

The broadband probe allows for the continuous measurement of Lambda values between 0.8 and 2.5.

These probes are installed as pre-catalyst sensors.