For catalyst testing, what results should you see with gases that can indicate a bad catalytic converter?

In the context of catalytic converter testing, a critical aspect to evaluate is how well the converter is functioning in terms of reducing harmful emissions. A catalyst that is functioning properly will effectively reduce the levels of nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons (HC).

High levels of NOx and high levels of CO in the exhaust gases are indicative of a failing catalytic converter. This scenario occurs because a malfunctioning converter isn't efficiently converting the harmful gases as intended. Instead, the NOx emissions remain elevated, reflecting incomplete combustion and poor management of nitrogen in the exhaust, while elevated CO levels indicate that the converter is not oxidizing carbon monoxide into carbon dioxide effectively.

In contrast, other combinations of exhaust gas levels would indicate a differently functioning catalytic converter. For instance, low levels of hydrocarbons combined with low levels of carbon monoxide suggest that the converter is working effectively, as it is breaking down both types of emissions. Thus, understanding the relationship between these gases is key to diagnosing catalytic converter performance.