About Lambda sensor fault

This is not exactly about DTM but maybe you know about it.
My car sometimes had the ECU error on and now with DTM I see that it is LAMBDA sensor. This usually happens when the car is cold or when after lots of pressure I drive it again normally.
I replaced the Lambda sensor but still happens sometimes. Does anyone have any thoughts about it? Also how the ECY understands faulty in lambda sensor cause even when faulty it shoes values.

My car is EVO 2 but with removed catalyst.

Lambda management is quite complex.

The error may be reported to various causes. Reports whether the signal comes out of a lot of parameters (and you can read values very often near to +/-20% which is the limit), or if the value is not provided by the ecu. If you try to send a fixed value of volts at the entrance of the ecu, simulating a lambda 1 value (and you read about the DTM the value 0), the ecu notice of this because it does not detect the correct value at various stages of the engine, and will give you error ...

So it is not always the sensor faulty but maybe my engine when cold gives strange values.
Thanks

nothing ;)