AutoCodes – Honda – P1420 Honda

P1420 Honda Code - NOx Adsorptive Catalyst System Efficiency Below Threshold

Quick Answer

The NOx Adsorptive Three-Way Catalytic Converter (TWC) absorbs NOx created during lean-burn running when the oxygen concentration is high. Common causes include Faulty NOX Three-Way Catalytic Converter (TWC), FaULTY Secondary HO2S (Sensor 2), fAULTY Third HO2S (Sensor 3). Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P1420 Honda indicates NOx Adsorptive Catalyst System Efficiency Below Threshold.
Common causes: Common causes include Faulty NOX Three-Way Catalytic Converter (TWC), FaULTY Secondary HO2S (Sensor 2), fAULTY Third HO2S (Sensor 3).
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 20,723

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 03, 2020

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
Comments
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Code P1420 Honda Description

The NOx Adsorptive Three-Way Catalytic Converter (TWC) absorbs NOx created during lean-burn running when the oxygen concentration is high. Then the engine is put into a richer running mode where the oxygen concentration and NOx levels are low, and the absorbed NOx is released, keeping the average NOx emissions low. The Diagnostic Trouble Code (DTC) will set when the NOx Adsorptive Catalyst Efficiency is below the threshold.

OBDII Code P1420 Honda - NOx Adsorptive Catalyst System Efficiency Below Threshold - AutoCodes.com — P1420 Honda Code - NOx Adsorptive Catalyst System Efficiency Below Threshold

What does this mean?

What are the Possible Causes of the DTC P1420 Honda?

Faulty NOX Three-Way Catalytic Converter (TWC)
FaULTY Secondary HO2S (Sensor 2)
fAULTY Third HO2S (Sensor 3)
Software update

How to Fix the DTC P1420 Honda?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

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 P1420

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1420 Honda code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.