02 sen codes on 0BD11 systems check for open, shorted , heater amp draw , and cross count , so a trim code without a 02 code is highly unlikely an indicator of a bad O2 sensor.
A lone trim code usually means the ECU is getting trim inputs , but it can not correct for them b/c they are out of the limitations of correction.
This can mean too much fuel [ like a bad fuel pressure regulator] or too much air [ like a vac leak or unmetered intake air to the engine, like an air leak after the MAF, between the intake and MAF]
.and finally, just a bad MAF not responding to the intake air mass .
Baically, the problem is a/f mix is beyond the capacity/limits of the system to correct...so a code pops telling you it is trying to correct an a/f mix problem, but the problem is beyond it's engine management parameters/limits to correct.....ie-getting too much air or fuel , depending on which trim code shows up...