I have a 1998 Boxster and the check engine light just came on. I scanned it and got codes: 1123 and 1125. I checked online and it looks like 2 of the O2 sensors. I just need to know if it is the two before or after the catalytic converter?

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1123 and 1125 are fuel trim fault codes, your car is running too rich. I would check the mass airflow reading with a scan tool. Should be 15-17 kg/h at idle warm with the a/c off. If it is too high, replace the mass airflow sensor. If it is in spec, check fuel pressure, it could be too high but that is VERY rare. This is most likely a fault with the mass airflow sensor.

- Casey