Hi,
The first things I recommend checking are the heat shields on the exhaust system as well as the catalytic converter.
Often times the heat shields will come loose or break and rattle at a specific RPM. However, that wouldn't set the check engine light. What I suspect is that the internal components in the catalytic converter are loose. If that is the case, you can hear a rattle and if they partially block the exhaust airflow, it can have a rough idle and set the check engine light.
Do this. Take a rubber mallet and tap on the exhaust to see if you can reproduce the sounds. Have a helper locate the source of the sound.
If you look below, I attached a pic of the exhaust system. I highlighted the catalytic converter and circled all the heat shields.
I hope this helps. Let me know if you have other questions.
Take care,
Joe
See pic below.
Image (Click to make bigger)
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Monday, January 17th, 2022 AT 7:12 PM