Misfire catalytic converter damage can escalate fast. Always ask how long it’s been misfiring and inspect the converter.

Q: I have a 2010 Honda CR-V. Last month its check engine light came on. I’m a retired mechanic and, using my diagnostic scanner, found a trouble code of P0420, which indicates an issue with c… ...

P0420 is the generic code that was likely stored in your vehicles computer to indicate that the catalytic converter efficiency is below the manufacturer's specified threshold.

P0420 code represents “Catalyst System Efficiency Below Threshold, Bank 1.” It is usually, but not always, caused by a bad converter that’s not reducing emissions output as it should.

Question:I have a 2001 Jeep Grand Cherokee with the 4.0-liter six-cylinder and about 120,000 miles. I keep getting a catalytic converter code P0420. I heard there may be a way to fix it by spacing ...

I'm a retired mechanic and my scanner found code P0420 — catalytic converter efficiency. I tried a catalytic converter cleaner. It worked for about two weeks and the light came back on.