Troubleshooting

DTC P0420 Catalyst System Efficiency Below Threshold (Bank 1)

CIRCUIT DESCRIPTION

DTC Detecting Condition:

The ECM compares the waveform of the heated oxygen sensor located behind the catalyst to determine whether the catalyst performance has deteriorated.

If the catalyst functions normally, the waveform of the heated oxygen sensor located behind the catalyst switches back and forth between rich and lean much more slowly.
When the waveform of the heated oxygen sensor located behind the catalyst alternates flutteringly between rich and lean, it indicates the catalyst performance has deteriorated.





CONFIRMATION DRIVING PATTERN

(a) Warm up engine.
(b) Drive the vehicle at 40 - 55 mph (64 - 88 km/h) for 4 minutes.
(c) Drive the vehicle allowing speed to fluctuate between 35 - 45 mph (56 - 72 km/h) for 16 minutes.

NOTICE: Drive with smooth throttle operation and avoid sudden acceleration.





INSPECTION PROCEDURE

HINT: Read freeze frame data using hand-held tester or OBD II scan tool, as freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.