Circuit Description

PCM monitors converter efficiency by comparing the voltage values of O2S1 and HO2S2. Under normal operating conditions, the O2S1 should vary between 10-999 mV and HO2S2 should remain relatively steady between 500-800 mV. This steady reading of the HO2S2 indicates a correctly functioning catalytic converter. When all parameter have been met, PCM will run this DTC diagnostic at idle. PCM will command rich or lean and monitor the time it takes the HO2S2 to go rich or lean. The longer it takes the HO2S2 to change rich/lean means the converter is storing oxygen and functioning properly.

PCM will usually run a 5 seconds test to determine the efficiency of the converter. If this test fails, PCM may take several tests during several ignition cycles to set this DTC. DTC will set when PCM has determined that the catalytic converter is no longer efficient by using the O2S1 and HO2S2 data when engine run time is greater than 9 minutes, engine speed between 650-900 RPM, engine speed greater than 1200 RPM for 30 seconds after closed-loop, calculated converter temperature is 707-1382°F (375-750°C), VSS at zero, closed-loop status, MAP change is less than 6 kPa and no CMP, CKP, ECT, EGR, EVAP, HO2S, IAT, O2S, fuel trim DTCs have been set.