Bank 1

[Amber]

A friend of mine with a 9th gen hit an armadillo, and immediately had the check engine light come. After taking it to Autozone it produced the famous P0420 code. The receipt / slip defining the problem says, "Catalyst system efficiency below threshold - bank 1."

I'm assuming bank 1 is the pre-cat sensor. Am I right?

[fishexpo101]

Should be looking at the sensor number - the Corolla would only have a single bank, Bank 1, but two sensor locations:

Bank 1, Sensor 1 = Pre-Cat O2 sensor
Bank 1, Sensor 2 = Post-Cat O2 sensor

I'd suggest they reset the CEL and see if it comes back. If it does, start looking for exhaust leaks around the frontpipe / catalytic converter area. More than likely, that Armadillo damaged the exhaust, causing the downstream (post-cat) O2 sensor to read too closely to the main O2 sensor. Making it appear that the cat is bad.

In 90% of the P0420 cases, the catalytic converter was perfectly fine - it was either an exhaust leak or bad connection to the O2 sensors that was causing this CEL to come on.

[Amber]

I was thinking the maybe the rear sensor was damaged by the armadillo. But I haven't looked under my car to see where the rear sensor is located. So ... that's my next question.

Is the rear sensor located where it could be contacted by road kill?