This is not always true (I also explained in previous forums) and I will explain: for example a fault lamp is on and I connect a diagnostic computer to an OBD socket and I see fault number P0403 and as you say I replace the exhaust gas cycle valve and still the fault exists it means not always reality (theory) reflects The practical and it means what exactly a professional person should perform before starting the sensor replacement and it means first check engine management software update (first stage), second stage check the sensor resistance at um meter and then draw conclusions. I if experience over 30 years in the automotive industry know in 100% garages replace parts only because a diagnostic device recorded a certain fault and like a straight mechanic / technician parrot replaces the part and it is incorrect and mismanagement. Any person who will be working very hard for a livelihood and it does not make sense that unprofessionalism will come on the client’s pocket. The sensors can show some malfunction but does not necessarily mean that the sensor is not working properly because the sensors are noisy from signals from additional sensors and this can be confusing, so as I explained above should be super professional and work in stages.

This is not always true (I also explained in previous forums) and I will explain: for example a fault lamp is on and I connect a diagnostic computer to an OBD socket and I see fault number P0403 and as you say I replace the exhaust gas cycle valve and still the fault exists it means not always reality (theory) reflects The practical and it means what exactly a professional person should perform before starting the sensor replacement and it means first check engine management software update (first stage), second stage check the sensor resistance at um meter and then draw conclusions. I if experience over 30 years in the automotive industry know in 100% garages replace parts only because a diagnostic device recorded a certain fault and like a straight mechanic / technician parrot replaces the part and it is incorrect and mismanagement. Any person who will be working very hard for a livelihood and it does not make sense that unprofessionalism will come on the client’s pocket. The sensors can show some malfunction but does not necessarily mean that the sensor is not working properly because the sensors are noisy from signals from additional sensors and this can be confusing, so as I explained above should be super professional and work in stages.