What condition of the catalytic converter would lead to vehicle rejection?

A catalytic converter plays a vital role in reducing harmful emissions from a vehicle's exhaust system. When a catalytic converter is bypassed or modified, it compromises its ability to function correctly, violating environmental regulations and safety standards. This condition will result in a vehicle being rejected during an inspection because it indicates that the emissions control system is not working as intended, which can lead to increased pollution.

While a securely attached catalytic converter and one located correctly in the exhaust system are crucial for optimal operation, these aspects alone do not determine the acceptance or rejection of a vehicle in an inspection. Additionally, a catalytic converter not operating under high temperature may impact performance but does not necessarily signify it has been bypassed or modified. In contrast, any modification or removal of the catalytic converter fundamentally alters its intended function, leading to rejection during an inspection.