Please list which engine you have when there's an engine-related problem. I looked these codes up for a 2.5L engine, non-hybrid. There's two versions of diagnostic charts, depending on the date the vehicle was manufactured. Both are about 30 pages long.
P0420: Catalyst System Efficiency Below Threshold Bank 1 (SFI System, A25A-FKS) [06/2017 - 08/2018]
I can offer a condensed version of what it takes to set this code. You may be able to verify this with your scanner. Look under the "Live data", "Sensor data", or something similar under the "Engine" menu. In that live data, look for the oxygen sensor readings.
During normal operation, if there's too much unburned oxygen in the exhaust gas, the front, or "upstream" oxygen sensor develops a voltage to indicate how much, but it can't measure a lack of unburned oxygen. Instead, the Engine Computer commands a fuel / air mixture that's too lean, then too rich. That switching action occurs roughly two times per second. Based on the length of time it's in one state, the computer can calculate the average time the mixture is in each state, and it makes adjustments in the length of time it pulses the injectors open.
During the lean state, the unburned oxygen gets stored in the catalyst material in the catalytic converter. During the rich state, the excess fuel is combined with the stored oxygen and gets burned so the fumes don't go out as pollution. When this process is working properly, the exhaust gas leaving the catalytic converter will be slightly rich for quite a while, then slightly lean, also for a long time. The switching rate might be as long as once every minute or two. The front sensor reading switches rapidly. The rear, or "downstream" sensor changes very slowly. That is what tells the Engine Computer the catalytic converter is doing its job.
Given the low mileage you listed, I suspect some type of contamination is the more likely cause. It's too soon to expect a normal failure. Most import catalytic converters have no trouble lasting 200,000 to 300,000 miles.
Sunday, March 8th, 2026 AT 4:47 PM