P0420

DTC P0420 Catalyst System Efficiency Below Threshold

CIRCUIT DESCRIPTION
The ECM observes the waveform of the heated oxygen sensor located behind the catalyst to determine whether the catalyst is performance has deteriorated.
If the catalyst is functioning 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 flatteringly between rich and lean, it indicates that catalyst performance has deteriorated.






CONFIRMATION DRIVING PATTERN
(a) Connect the hand-held tester to the DLC3.
(b) Clear DTC.
(c) Warm-up the engine.
(d) Drive the vehicle at 40 - 55 mph (64 - 88 km/h) for 4 minutes.
(e) Drive the vehicle allowing speed to fluctuate between 35 - 45 mph (56 - 72 km/h) for 16 minutes.
(f) Check pending DTC.

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






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