Mike's Workshop Manuals
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Hyundai
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2004
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Elantra GLS, Standard
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Repair and Diagnosis
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Engine Performance
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Engine Control Systems
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Fuel System
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DTC Trouble Shooting Procedures
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DTC P0420: Main Catalyst Efficiency Below Threshold (Bank 1)
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Inspection Procedures
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4. Check HO2S
4. Check HO2S
Check front and rear HO2S for normal operation.
Refer to
DTC P0131
-
DTC P0140
for a detailed procedure.
Are front and rear HO2S normal?
Yes: Go to next step.
No: Replace it.