Catalytic converter, heat shield, and check engine light

Hi all,

I have a 1999 Honda CR-V with 90,000 miles. Last week, my catalytic converter heat shield was removed because it was rattling. No big deal, right? Well, 5 days later, my check engine light came on with the code P0420, meaning a catalytic converter problem.

Is it possible that removing the heat shield caused a fluctuation in the temperature enough to give a false reading to the catalytic converter sensors and thus trip the check engine light, or is it merely a coincidence, and the catalytic converter needs to be replaced? Is this sort of thing even possible?


The heat shield’s purpose is to keep the heat of the converter away from other stuff like grass or the car’s body, not keep heat in, so removing the heat shield should have no effect on the converter’s performance.

I’d guess what probably happened is the converter got whacked at some point, loosening the heat shield and causing internal damage to it. You might also crawl under there and double check that the heat shield didn’t take a chunk of the converter’s shell with it when it was removed, because an air leak could trigger the code.

The heat shield protects the vehicle from the heat of the converter, and should NOT be removed. A loose, rattling heat shield should be tightened or repaired, but never removed. The floor of your CR-V could get hot enough to set the carpet padding on fire in the interior.

Please ask whoever removed the heat shield to re-install it tightly so it no longer rattles.

The check engine light is a coincidence, unless the converter was damaged, as GreasyJack suggests.

Or maybe a wire to the sensor or the sensor was damaged accidentally when they were working on it.