Which emissions result can signify a defective catalytic converter upon smog testing?

A defective catalytic converter can lead to high emissions, particularly in hydrocarbons (HC) and carbon monoxide (CO). During smog testing, elevated levels of these emissions indicate that the catalytic converter is not properly converting harmful gases into less harmful substances.

In the scenario presented, the result with HC at 210 ppm and CO at 2.8% signifies a concern because both of these values are significantly higher than typical emissions levels. Catalytic converters are designed to reduce the output of HC and CO; therefore, if these numbers are elevated, it suggests that the converter is failing to perform its essential function of oxidation and reduction.

Hydrocarbon levels above 200 ppm are particularly alarming, as they exceed the acceptable limits, indicating incomplete combustion of fuel and ineffective treatment of exhaust gases. Moreover, while CO is a natural byproduct of combustion, 2.8% is also indicative of inadequate conversion from the catalytic process.

Overall, the readings suggest that the emissions are not being adequately reduced, pointing directly to a potentially malfunctioning catalytic converter. This combination of high HC and CO levels is a clear sign that the emissions control system may not be functioning correctly.