P0420 error CEL Catalyst System Efficiency Below Threshold

[zape]

Has anyone experienced this? What would be the cause? How to solve?
Currently have ~100K miles on the car

 

[EdP]

Has anyone experienced this? What would be the cause? How to solve?
Currently have ~100K miles on the car

Could be O2 sensors or could be the catalytic converter is not working properly. Check for physical damage or leaks in the exhaust system, check the connections to the sensors. Even poor combustion from a defective injector can cause a change in the efficiency of the cat. At least check other parts before replacing the cat as other things can affect it. Given the miles, I'd change the plugs if they have not been already. You could be dumping a lot of unburned gas out the pipe.

 

[Suburbazine]

the CEL is determined by comparing the switching speed ratio between the front and the rear O2S on each side. When the rear sensor reaches a ratio too close to the front sensor, it triggers the warning. It's not a totally useful warning either, as aging sensors can switch slower (in the case of the front which is exposed to a lot of heat) or switch faster (in the case of the rear sensors which are exposed to contaminants).

Normally I would recommend replacing the front O2S relevant to the code- P0420 is Bank 1 so I'd be replacing the passenger front O2S first.

 

[zape]

Just wanted to add that the error appears infrequently, maybe once a month. Often soon after I go to a car wash.

They recommended fuel system induction cleaning at the dealership. Do you think this procedure may help? Is this the same as intake valves cleaning from the carbon deposits or something else?

 

[EdP]

Just wanted to add that the error appears infrequently, maybe once a month. Often soon after I go to a car wash.

They recommended fuel system induction cleaning at the dealership. Do you think this procedure may help? Is this the same as intake valves cleaning from the carbon deposits or something else?

Two possibilities I can think of from the car wash. Water spray is cooling the cat so it is not operating efficiently or water is causing one of the O2 sensors to not work properly. Has it ever happened driving in the rain?

No idea if the induction system would help but anything that changes the fuel mixture is a possibility. I would check the connections on the sensors first.