P0420 HONDA - Catalyst System Efficiency Below Threshold Bank 1
P0420 HONDA Possible Causes
- Faulty Three-way Catalyst Converter Bank 1
- Exhaust Tube
- Intake Air Leaks
- Faulty Oxygen (O2) Sensor
- Faulty Fuel injector(s)
- Leaking Fuel Injector (s)
- Faulty Spark plugs
- Improper Ignition Timing
- Faulty Engine Control Module (ECM)
- Dirty Air Filter
How do I fix code P0420 HONDA?Check the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.
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There is a Factory Service Bulletin for the following Honda models:
2003–2005 Honda Civic Hybrid ULEV (KA)
2002–2006 Honda Insight With M/T
Honda Civic, Insight Factory Service Bulletin OBDII Code P0420
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Cost of diagnosing the P0420 HONDA code
Labor: 1.0The cost of diagnosing the P0420 HONDA code is 1.0 hour of labor. The auto repair's diagnosis time and labor rates vary by location, vehicle's make and model, and even your engine type. Most auto repair shops charge between $75 and $150 per hour.
When is the code detected?- Three way catalytic converter Bank 1 does not operate properly.
- Three way catalyst converter Bank 1 does not have enough oxygen storage capacity.
- Engine Light ON (or Service Engine Soon Warning Light)
P0420 HONDA DescriptionThe Engine Control Module (ECM) monitors the switching frequency ratio of heated oxygen sensors 1 (front O2 sensor) and heated oxygen sensors 2 (rear O2 sensor).
A three-way catalyst converter (Manifold) with high oxygen storage capacity will indicate a low switching frequency of heated oxygen sensor 2. As oxygen storage capacity decreases, the heated oxygen sensor 2 switching frequency will increase.
When the frequency ratio of heated oxygen sensors 1 and 2 approaches a specified limit value, the three-way catalyst malfunction is diagnosed.
More InformationNeed more information on how to fix the P0420 HONDA code?
Get Access to Factory Service Manuals
Information for specific Honda models
Need more help?Get the P0420 Honda code diagnosed by a professional: Find a repair shop in your area
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