P0420 on Honda Odyssey
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 Odyssey 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 Odyssey
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 Odyssey Owner Reports
Source: NHTSA Complaints Database
"Strong vibration felt in passenger compartment and steering wheel when driving at 40 to 45 mph. there was a droning noise as well. this has been an issue since 2010, but identified by dealer service advisor only in feb 2014. quoted 800 dollars to replace both front engine mounts."
"Honda issued a recall on the fuel pump December 2023. They did not have any parts available to replace mine. I had brought in my Odyssey Elite to Space Coast Honda multiple times before the recall stating my engine wouldn't crank. I was unable to get the fuel pump replaced until December 5, 2024."
"While driving, the check engine light appeared and the vehicle began running rough and hesitating during acceleration."
"Life-Threatening Acceleration Lag: The vehicle is experiencing severe power loss during critical driving moments, for example, while entering intersections or attempting to re-accelerate into moving traffic."
"The contact owns a 2019 Honda Odyssey. The contact stated that the emission warning light was illuminated. The vehicle was taken to an independent mechanic, where a diagnostic scanner was used to retrieve diagnostic trouble codes P0420 and P0430."
All reports filed by vehicle owners directly with the U.S. Department of Transportation.
📊 Complaint Trend by Model Year
Common Causes on Honda Odyssey
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.