21622 North 7th Avenue, Phoenix, AZ 85027
1. Oscilloscope Graph - We compare Upstream and Downstream waveforms, as graphed on a scanner or scope. The downstream oxygen sensor waveform should be much flatter and show much less activity than the upstream sensor.
2. Mode 6 - Consult Mode 6 for actual catalytic converter health measurements taken as the on-board computer went through the readiness process.
3. Check the Engine Codes - P0420 and/or P0430 trouble codes in computer memory. These engine codes are highly accurate indicator.
4. Converter Temperature Test - Exhaust gas temperatures exiting the converter should be 10% - 30% hotter than exhaust gases entering the converter.
5. Manifold Vacuum Test - Measure IDLE manifold vacuum; should be 18" - 22". Increase throttle input. Measure 3000 RPM manifold vacuum. Should have dropped initially; then, recovered to almost the same 18" to 22" reading. Low vacuum readings taken at 3000 RPM suggest exhaust restriction is present.
6. OBD 1 Emissions Fail Sheet - There are 3 failure parameters: HC, CO, and NOx. If the vehicle fails any two or more parameters, replace the converter. The reasoning is this...the only single solution that solves any two of the failure parameters is replacement of the Catalytic Converter.
7. Exhaust back Pressure Test - Normal exhaust back pressure should be less than 2 PSI. Thread a pressure gauge into the upstream oxygen sensor bung. Snap the throttle and monitor back pressure. Elevate steady rpm to 3000. Monitor back pressure.