i have a question; about 3 days ago a cel in my car appear and i send it to get scan and came up: DTC P0422 Catalyst System Low Efficiency Bank 1.
what's that means? that the catalytic is not working properly? and i have to change the catalytic? i have full exhaust and a magnaflow high flow catalytic.
the car wasnt move that much because i wasnt here (overseas), but my brother drove it from time to time not much. i clear the cel 2 days ago, normally comes back in 3 days or so. I will see if pop up again.

Thank you

It's indicating the O2 sensor is not working properly.That should be the oxygen sensor at the exhaust manifold u need to either check the connection or probably replace it. Bank 1 is that O2 sensor and for your info bank 2 is the O2 at the cat convertor not that it is relevant to your code that popped up.I would just replace the sensor at the exh manifold.If I am incorrect or left something off may others correct or add to this post.Just a note u may want to invest in a chiltons manual for future refer it shows the codes interpretations and what to check.It will cost about 18.00 at advance auto or auto zone and very useful for many other things u will need.

Ron Love wrote:It's indicating the O2 sensor is not working properly.That should be the oxygen sensor at the exhaust manifold u need to either check the connection or probably replace it. Bank 1 is that O2 sensor and for your info bank 2 is the O2 at the cat convertor not that it is relevant to your code that popped up.I would just replace the sensor at the exh manifold.If I am incorrect or left something off may others correct or add to this post.Just a note u may want to invest in a chiltons manual for future refer it shows the codes interpretations and what to check.It will cost about 18.00 at advance auto or auto zone and very useful for many other things u will need.

I PM'D you on this info. This is incorrect. Bank refers to the side of the motor (4 cylinders are always bank 1) If we have a V motor Bank 1 would be left or right, and Bank 2 the other). If it is referring to a certain sensor (O2 sensor) it will say Bank 1 sensor 1, or Bank 1 sensor 2. You can get this code for either of your O2 sensors. I have gotten it for a bad primary O2 and for my second O2 sensor when cat was removed. The only real way to tell is to hook up something that can read the O2 sensors and see what they are reading. Some people have had issues with high flow cats throwing this code. Some have also had issues with headers on the 2.4 and having a non heated O2 sensor. I have that issue and now run a heated O2 sensor on the header.



FU Tuning

The catalyst efficency monitor works by monitoring sensor 1 and comparing that too sensor 2. In theory, the 2nd o2 should read fairly close to 600 mv, fluctuating slightly. The front o2 sensor should fluctuate between 100 mv and 900 mv. Hooking a scan tool to the car, you can watch the 02 sensors cycle.

Generally, You should see the 02 sensors moving. Just because the front o2 stays abouve 900 mv at all times doesnt mean the sensor is bad either. Could just mean the car is overly rich and cant correct itself.

People have had problems with high flow cats messing with sensors. That is because those cats have less of the precious metals in them to burn the fuel and hold the oxygen. The original OEM cat off the car cost much more than the magnaflow. Its because of these precious metals. Rhodium, for example is about 1200 dollars an ounce. WQithout all these precious metals, the cat is less efficent therfore the computer might pick up on that.

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