Honda CR-V 1997 Service Manual page 402

Emission Control System
Three Way Catalytic Converter (TWC) (cont'd)
I P0420 I
The scan tool indicates Diagnostic Trouble Code (DTCI P0420: Catalyst system efficiency below threshold.
Description
This system evaluates the catalyst's capacity by means of the H02S (Primary and Secondary) output during stable driving
conditions. If deterioration has been detected during three consecutive driving cycles, the MIL comes on and Ole P0420 will
be stored.
NOTE: If some of the orcs listed below are stored at the same time as
Ole
P0420, troubleshoot those OTCs first, then
troubleshoot DTC P0420.
P0137, P0138: Secondary H02S (Sensor 21
P0141: Secondary H02S (Sensor 21 Heater
Possible Cause
• TWC Deterioration
• Exhaust system leakage
Troubleshooting Flowchart
- The MIL has been reported on.
- DTC P0420 is stored.
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Problem verification:
1. Do the ECM/PCM Reset Proce-
dure.
2. Start the engine. Hold the
engine at 3,000 rpm with no
load (in Park or neutral) until
the radiator fan comes on .
3. Connect the SCS service con-
nector.
4. Test-drive 40 - 55 mph (64 - 88
km/h) for approx. two minutes.
Then decelerate for at least 3
seconds with the throttle com-
pletely closed. Then reduce
the vehicle speed to 35 mph
(56 km/hL and try to hold it
until the readiness code
comes on.
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Is OTC P0420 indicated?
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YES
Check the TWC !see section 9).
If necessary. replace the TWC.
11-200
NO
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Intermittent failure. system is OK
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at this time.