P0420 on Honda Pilot
Catalyst System Efficiency Below Threshold Bank 1
Methodology: Reviewed against the SAE J2012 generic DTC definition and NHTSA owner-complaint patterns, then scoped to Honda Pilot context without treating complaints as confirmed diagnoses.
Sources: SAE/OBD-II definitions, manufacturer service information, and public reliability reports (including NHTSA where applicable).
- SAE J2012 Diagnostic Trouble Code Definitions — Generic diagnostic trouble code definition reference for P0420.
- NHTSA recalls, complaints, and manufacturer communications — Used to check public owner complaint context, recall status, and safety-related manufacturer communications by VIN or vehicle.
Limits: Guidance is informational and may not match every model-year or revision. Confirm with the official manual and diagnostics before replacing parts. For safety-critical or electrical work, use a qualified technician.
What P0420 Means on Your Honda Pilot
P0420 is a diagnostic trouble code indicating: Catalyst System Efficiency Below Threshold Bank 1. This code relates to the emission controls system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.
Real Honda Pilot Owner Reports
Source: NHTSA Complaints Database
"My vehicle suffered a catastrophic failure of the exhaust and engine systems directly caused by the defective fuel injection system identified in Service Bulletin 20-100."
"Check engine light on emissions system problem and transmission system problem, there is loss power of engine light, after 2 gear transmission feel like it jerks I don't have save to drive my car, i would like to request a recall to be inspected and repair by warranty of Honda because my car is de"
"My car got recall from Honda on: P0420 (rear bank catalyst system efficiency below threshold [bank 1]) P0430 (front bank catalyst system efficiency below threshold [bank 2]) P0300-P0306 (misfire) P219A (air-fuel ratio variation of cylinder [bank 1, rear bank]) P219B (air-fuel ratio variati"
"Honda has a known issue with its emissions. A warranty extension Service Bulletin 22-002 has been issued to replace fuel injectors up to 10 yrs 150,000 miles but they do not identify other malfunctioning components that also need replacement."
"Our 2016 honda pilot had a check engine light for fault code p0420. dealer diagnosis was faulty fuel injectors in cylinders 2 and 3. dealer replaced all 6 fuel injectors free of charge. it seems preposterous that any of the 6 fuel injectors had failed with only 41,632 miles on the odometer."
All reports filed by vehicle owners directly with the U.S. Department of Transportation.
📊 Complaint Trend by Model Year
Common Causes on Honda Pilot
Based on NHTSA complaint component analysis for this vehicle.
What To Do Next
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1
Check for recalls on YOUR VIN
Go to nhtsa.gov/recalls and enter your VIN. If your vehicle is covered, repairs are free.
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2
Get a proper diagnosis
A code alone doesn't tell you the exact failed part. A diagnostic at a shop ($50–$150) pinpoints the root cause before you spend money on parts.
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3
Compare repair quotes
Get 2–3 quotes. Dealer vs. independent shop prices often differ 30–50% for the same repair.