Catalytic Converter System Troubleshooting; Catalytic System Efficiency Below Threshold - Honda Civic 2002-2003 Service Manual

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Catalytic Converter System
DTe Troubleshooting
DTe P0420: Catalytic System Efficiency
Below Threshold
NOTE: If some of the OTCs listed below are stored at
the same time as OTC P0420, troubleshoot those OTCs
first, then recheck for OTC P0420.
P0137, P0138: Secondary Heated Oxygen Sensor
(secondary H02S) (Sensor 2)
P0141: Secondary H02S (Sensor 2) heater
1. Reset the ECM (see page 11-4), then continue to
step 2 through 5 to reset the readiness code.
2. Start the engine. Hold the engine at 3,000 rpm with
no load (in neutral) until the radiator fan comes on.
3. Drive for about 10 minutes without stopping. Your
speed can vary.
4. With the transmission in 4th gear, drive at a steady
speed between 50-62 mph (80-100 km/h) for
30 seconds.
5. Repeat step 4 three times. Between each repetition,
close the throttle completely for 1-2 seconds. If
the engine is stopped during this part of the
procedure, repeat steps 3, 4 and 5.
6. Check for a Temporary OTC with the scan tool.
Does the scan tool indicate Temporary OTe
P0420?
YES-Check the TWC. If necessary, replace the
TWC .•
NO-Check for readiness code completion. If the
readiness is complete, it was a intermittent failure,
and the system is OK at this time. If the readiness
code is incomplete, repeat steps 2 through 5 .•
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