Troubleshooting

DTC P0420 CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD

DTC Detecting Condition:

CIRCUIT DESCRIPTION
The ECM observes the waveform of the heated oxygen sensor located behind the catalyst to determine whether the catalyst 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 flutteringly between rich and lean, it indicates that catalyst performance has deteriorate





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.

Steps 1-2:

Steps 3-4:

INSPECTION PROCEDURE
Read freeze frame data using the hand-held tester or the OBD II scan tool, as freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, this 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.