I do get some that require a new catalytic converter, but this is only after long periods of driving a vehicle with problems whether it is gas type, worn spark plugs, vacuum leaks, clogged fuel filter, etc., and they are few. and far away.
Catalytic converters are designed to last for a large number of years as long as the engine operates as designed. Too rich or too lean kills them quickly, either by carbon build-up or overheating. If a catalytic converter is bad, you need to make sure it is bad and then find out what caused it to fail. Otherwise, you will destroy the new one.
And, some shops are quick to replace a CAT because they are actually cheaper than you think when bought in bulk or labor and the markup used is exceptional, then you have added labor which comes down to the profit margin. A new cat will burn more efficiently than a used one and mask an engine performance problem. These stores know this. Some may not and are under the impression that a 420 code is a dead giveaway.
If the check engine light comes back on for P0420 Catalyst Efficiency Below Threshold, go through the list and check everything on it first.
When I get into a vehicle with a bad CAT, which may take a while, I’ll post a video of the data so you can see the difference in ECM feedback and you’ll understand what I’m talking about. And, sensor data is available on many low-cost scanners you can buy at a parts store.
