1. Replace the oxygen sensor. The oxygen sensor is responsible for monitoring the amount of oxygen in the exhaust gas. If the oxygen sensor is not working properly, it can cause the engine to run rich or lean, which can in turn cause the catalytic converter to malfunction.
2. Replace the catalytic converter. The catalytic converter is responsible for converting harmful pollutants in the exhaust gas into less harmful substances. If the catalytic converter is not working properly, it can cause the P0421 code to be set.
3. Check the exhaust system for leaks. Exhaust leaks can cause the oxygen sensor to read incorrectly, which can in turn cause the P0421 code to be set.
4. Check the fuel injection system. A faulty fuel injector can cause the engine to run rich or lean, which can in turn cause the catalytic converter to malfunction.
5. Update the vehicle's software. In some cases, a P0421 code can be caused by a software issue. Updating the vehicle's software can fix this issue.
It is important to note that the P0421 code is a generic code, which means that it can be caused by a variety of different problems. If you are not comfortable diagnosing and repairing automotive problems, it is best to take your Hyundai Santa Fe to a qualified mechanic for diagnosis and repair.
