I am getting code 72 on my mom’s 1997 Intrepid 3.5L. Code 72 means “Catalytic Converter Efficiency Below Required Level”. My mom just recently had a new EGR valve put in because the light was on . . .and now it’s on again . . .code 72. Could the sensor or connection be bad causing this to happen? There is no emissions testing here in Wisconsin so the converter’s efficiency is not an immediate concern. How do I clear the codes . . .unhook the battery?
Thanks,
Matt

disconnecting the battery will clear the code from memory, but you have a hard code, that means everytime you clear that code, it resets because there's a serious fault found that could cause catalytic converter damage. Even if the EGR were bad, it would set a code for that. Sounds like you need to replace the catalytic converter(s).