OBD code P0301,P0430 and P0174?

This is noticed on Lexus Ls430 car.It has run more then 300000 miles.
First the error code P0301 came.Its a number 1 cylinder misfire error code.The customer tested the cylinder and replaced the number 1 cylinder, but still obd code P0301 is coming up and including that error code P0430 and P0174 also came.This other two codes came after cylinder 1 was replaced.Previously only one misfire code P0301 was there.

On basis of that the troubleshooting for the problem is as follows :-----


As far as the answer goes regarding the P0301 code that probably would be difficult to determine given everything you've done and using propane and gasoline combinations. Short of doing a cylinder compression test that's about the only thing I see that you have not done. The cylinder compression should show approx 180psi.

The P0430 code means the catalytic converter for bank two has failed. This could be a false code because the P0174 code is indicating a lean condition. On bank two when this happens it can cause problems in the catalytic converter and could be setting this code because the rear 02 sensor is not functioning correctly due to the lean condition. Catalytic converter failures with this kind of mileage is not uncommon. Any cylinder misfire causes unburned fuel to be burned in the catalytic converters. This is what actually damages the converters. Because cylinder one is the one that has been misfiring you would think it would be setting a P0420 code which is the catalyst efficiency code for bank one.

Also i suggest try cleaning the mass airflow sensor and make 100% certain that you have no intake leaks that could be directing unaccounted for air into bank two. This is the opposite bank that hold cylinder number one that your misfire is in. If you continue to drive the vehicle with the cylinder one misfire and the check engine light starts to flash you will eventually damage bank one converter.

This details will help you to troubleshoot the issue and confirm the problem.So you can go for repairing in that way.

Thanks.

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