- Install scan tool. Start engine and check if DTC P0420 is present. If DTC is present, go to next step. If DTC is not present, problem is intermittent.
- Check for exhaust leak before and after the catalytic converter. Repair as necessary. If leaks are not found, check rear O2S. For diagnosis, see related DTC or «SYSTEM/COMPONENT TESTS»(ref-16580) article. Replace as necessary. If rear O2S is okay, go to next step.
- Replace catalytic converter. Clear DTC. See «CLEARING DTC(S)»(ref-16579-S36162508062000122900000) . Retest system. If DTC resets, replace ECM.
Home/Hyundai/Elantra/Hyundai Elantra II (1995-1998)/Repair manual/Testing & Diagnostics/DTC P0420 - CATALYST EFFICIENCY BELOW THRESHOLD
Contents
Wiring diagrams Section: Testing & Diagnostics- Engine Controls - Tests W/codes: Diagnosis
- Engine Controls - Tests W/codes: Component Locations
- Engine Controls - Tests W/codes: Other
- DTC P0102/P0103 - MASS AIRFLOW (MAF) SENSOR CIRCUIT INPUT
- DTC P0112/P0113 - INTAKE AIR TEMPERATURE (IAT) CIRCUIT
- DTC P0116/P0117/P0118 - ECT SENSOR CIRCUIT
- DTC P0122/P0123 - THROTTLE POSITION (TP) SENSOR CIRCUIT INPUT
- DTC P0130/P0131/P0132/P0137/P0138 FRONT & REAR O2S SENSOR CKT
- DTC P0133 - FRONT O2S CIRCUIT SLOW RESPONSE
- DTC P0134/P0136 - O2S CIRCUIT, NO ACTIVITY DETECTED
- DTC P0135/P0141 - O2S HEATER CIRCUIT MALFUNCTION
- DTC P0201/P0202/P0203/P0204 - INJECTOR CIRCUIT MALFUNCTION
- DTC P0300 - RANDOM MISFIRE DETECTED
- DTC P0301/P0302/P0303/P0304 - CYLINDER MISFIRE DETECTED
- DTC P0326 - KNOCK SENSOR (KS) CIRCUIT RANGE
- DTC P0335/P0336 - CKP SENSOR CIRCUIT RANGE/MALFUNCTION
- DTC P0342/P0343 - CMP SENSOR CIRCUIT MALFUNCTION
- DTC P0420 - CATALYST EFFICIENCY BELOW THRESHOLD
- DTC P0442/P0443/P0446/P0455 - EVAP PURGE CONTROL SYSTEM
- DTC P0444/P0445 - EVAP PURGE CONTROL VALVE CIRCUIT
- DTC P0447/P0448 - EVAP VENT CONTROL VALVE CIRCUIT
- DTC P0451 - FUEL TANK PRESSURE SENSOR SIGNAL NOT VALID
- DTC P0452/P0453 - FUEL TANK PRESSURE SENSOR MALFUNCTION
- DTC P0501 - VEHICLE SPEED SENSOR (VSS) RANGE
- DTC P0506/P0507 - IDLE RPM IS NOT AS SPECIFIED
- DTC P0605 - INTERNAL CONTROL MODULE ROM ERROR
- DTC P1123/P1124/P1127/P1128 - AIR/FUEL RATIO CONTROL
- DTC P1510/P1513/P1552/P1553 - ISC ACTUATOR CIRCUIT
- DTC P1586 - ENCODING SIGNAL CIRCUIT OUT OF RANGE (A/T & M/T)
- DTC P1605/P1606 - ACCELERATION/ROUGH ROAD SENSOR CIRCUIT
- DTC P1611/P1614 - MIL REQUEST SIGNAL CIRCUIT
- Engine Controls - System/component Tests: Overview
- Engine Controls - System/component Tests: Diagnosis
- Engine Controls - System/component Tests: Other
- Abbreviations
- Accessory Drive Belts
- Adjustments
- Airbag
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- Application
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- Basic Trouble Shooting
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- Electrical Component Locations
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- Engine Performance
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- General Servicing - All Makes
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- Identification
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- Wiring Diagrams - Engine Performance