EGR / AGR stands for Exhaust Gas Recirculation.
The system redirects a controlled amount of exhaust gas back into the intake system.
One of its main purposes is to help control combustion temperatures and reduce NOx formation.
Over time, EGR systems can become affected by carbon deposits and mechanical problems.
For example, if an EGR valve cannot reach the requested position, the ECU may detect an airflow value
that does not match its expected model.
This can lead to:
EGR-related faults,
airflow-related faults,
poor drivability,
reduced performance.
Diesel
EGR is extremely common on diesel engines.
Petrol
Some petrol engines also use exhaust-gas recirculation strategies, but the system design can be quite
different.
That is why an EGR-related fault should not automatically be interpreted as a software problem.