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Symptom: P0420-CATALYTIC 1/1 EFFICIENCY When Monitored and Set Condition: P0420-CATALYTIC 1/1 EFFICIENCY When Monitored: Engine Run time greater than 90 seconds. Engine Coolant greater than 70°C (158°F) Vehicle speed greater than 20 MPH and less than 55 MPH. Engine Speed 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: A new rear O2 Sensor along with an aging front O2 Sensor may cause t, read DTCs and record the related Freeze Frame data. Is the Good Trip Counter displayed and equal to zero? All Yes → Go To 2 No → Refer to the INTERMITTENT CONDITION symptom in the Driveability category. 153 DRIVEABILITY - NGC |