Catalytic Converter: Testing and Inspection

Upstream of the catalytic converter is a test port for connecting a CO meter.
1. Run engine to operating temperature.
2. Unscrew the test port cap and connect a CO meter.
3. Measure and note CO content.
4. Remove CO meter and screw on test port cap.
5. Measure and note CO content at tailpipe.
6. Compare the two reedings. CO content should be substantially lower at tailpipe outlet.
7. Replace catalytic converter if readings are identical.

An additional testing method can be used to test the converter visually. Remove the catalytic converter from the vehicle. With either opening towards a light source, inspect the ceramic or metal insert from both sides. If the insert is broken, melted or clogged, the catalytic converter must be replaced.