2005 Toyota Camry: OBD Code P0420?

Error code Stored in Cars Engine computer module.Also known as ECM or ECU.
Scanning the computer with OBD II Scan tool shown Error Code P0420.

The details for this error code are as follows:----


P0420 catalyst system efficiency below threshold (Bank 1)

This is likely to be a faulty catalytic convertor.

On 2005 Toyota Camry there are 3Catalytic converter.

It is impossible to find out which one is at fault without proper testing of Each Converter.

This Basics has to be inspected on Each Converter one by one:--------
The Causes for Catalytic converter to get faulty:---------



Catalytic converter has failed (check for physical damage and discoloration)
Check for air leaks in the Air Induction system (e.g., in the intake manifold)
Check for air leaks in the exhaust manifold and in the exhaust pipes
AFS 1/1 is loose in its mounting hole
AFS 1/1 has failed (it may be contaminated with fuel, silicone or water)
HO2S 1/2 has failed (it may be contaminated with fuel, silicone or water)

As per ?My Garage Experience in most of such cases,the rear one Catalytic Converter fails more often. But most of the shops will recommend replacing all 3.

There is one more best and simple option to confirm the problem.And that is by using a handheld computer to check the system.
For this procedure,first verify that the fuel trims on both banks are good at idle and when driving the vehicle.
But if you notice that the fuel trim is not correct then in that case you need to check/inspect the Mass Air Flow sensor. It is possible to have fuel trim at 20% and not set a fuel trim code and cause the catalytic converter to not function properly. BUT,

If the fuel trim is only off on one bank Then in that case  look for a faulty/dirty Air Fuel Ratio sensor, Also a possibility of vacuum leak or a fuel delivery problem on the bank the fuel trim is off.

But If all checks ok and if the fuel trim is good and within 10% plus or minus, drive the vehicle at a steady throttle, steady cruise and monitor the rear O2 sensor operation. Now if the rear O2 sensor is switching rich to lean, the catalytic converter is not storing oxygen correctly. When the catalytic converter functions correctly, the rear O2 sensor should not switch. If the rear O2 sensor switches at a steady cruise while driving, the catalytic converters are failing.
Since this vehicle uses Air Fuel Ratio sensors instead of front O2 sensors, if the vehicle has high mileage, it is always wise to replace the front AF ratio sensors, if the catalytic converters are faulty and need to be replaced. In some cases, the AF ratio sensors can cause a false P0420 code.

This details will help to test and confirm the problem.

Hope All goes Well.
Thanks

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