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Symptom: P0420-1/1 CATALYTIC CONVERTER EFFICIENCY When Monitored and Set Condition: P0420-1/1 CATALYTIC CONVERTER EFFICIENCY When Monitored: After engine warm up to 70°C (158°F), 180 seconds of open throttle operation, at a speed greater than 18 mph and less than 55 mph, with the engine at Set Condition: As catalyst efficiency deteriorates, the switch rate of the downstream O2 sensor approaches that of the upstream O2 sensor. If at any point during the test the POSSIBLE CAUSES GOOD TRIP EQUAL TO ZERO VISUALLY INSPECT CATALYTIC CONVERTER EXHAUST LEAK ENGINE MECHANICAL CONDITION AGING O2 SENSOR CATALYTIC CONVERTER TEST ACTION APPLICABILITY 1 NOTE: If a O2 Sensor DTC(s) set along with the Catalytic Converter t, read DTC’s. Is the Good Trip displayed and equal to zero? All Yes → Go To 2 No → Refer to the INTERMITTENT CONDITION symptom in the Driveability category. 2 Inspect the Catalytic Converter for the following damage. All Yes → Replace the Catalytic Converter. Repair the condition that may have caused the failure. No → Go To 3 115 DRIVEABILITY - SBEC |