P0420
107 owner reports and 553 manufacturer filings across 196 model years from Acura, Buick, Cadillac, Chevrolet and others.
Where P0420 shows up
Source: NHTSA manufacturer communications and complaintsShowing the 60 model years where P0420 appears most; it is on file for 196 in total.
A model year appears here because the code is named in its record, not because every one of these vehicles sets it. Counts are mentions in the federal files, not failure rates — nobody publishes the denominator.
What it gets filed under
When owners report it
miles, typically
Half of the 18 owner reports naming P0420 that carry an odometer reading fall between 50,000 and 119,000 miles. A code that shows up at 30,000 miles is a different proposition from one that shows up at 130,000, and that difference is the single most useful thing in this record.
What owners said
Source: NHTSA complaint databaseOwners’ own words, one per nameplate, scrubbed of anything identifying. These are unverified reports filed with NHTSA — they are what was said, not a finding that it was true.
After the engine replacement, the vehicle developed additional drivability and warning-light concerns, including P0420 and communication/CAN faults
The codes pulled were P0217, P0303, P0316, P0420, and P06E9 - overheat, misfire, misfire, catalyst efficiency, and turbocharger coolant/fluid, all consistent with the coolant intrusion pattern described in TSB 22-2229
P0420 P0441 P0014 P1326 C1260 C1688 C2130 These are the codes that's affecting my car
The vehicle has been to an authorized dealer over 21 times.SAFETY RECALL NEGLIGENCE & POWERTAIN DAMAGE: At 95k miles, the vehicle displayed active check engine codes P0087 (Low Fuel Pressure), P0420, and P0430
Condition: The vehicle must display a Malfunction Indicator Light (Check Engine Light) with specific stored fuel-system error codes (such as P0300 through P0306, P0420, P0430, P219A, or P219B)
Manufacturer filings that name it
Source: NHTSA manufacturer communicationsService bulletins and campaigns whose filed summary names P0420. Quoting the document number at a service desk is often the fastest route to a diagnosis someone has already written down.
- 18-073-262026-07-22 · Engine
- Flash: Powertrain Control Module (PCM) Updates Customers must experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle exhibit/set SYMPTOM: one or more of the following Diagnostic Trouble Codes (DTCs): â—� P0420 - Catalyst System Efficiency Below Threshold Bank 1. â—� P0430 - Catalyst System Efficiency Below Threshold Bank 2. â—� P0556 - Brake Booster Pressure Sensor Circuit Perf
- 18-063-262026-06-25 · Engine
- Flash: Powertrain Control Module (PCM) Updates Customers must experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle must exhibit/set one or more of the following Diagnostic Trouble Codes (DTCs): â—� P0420 - Catalyst System Efficiency Below Threshold Bank 1. â—� P0430 - Catalyst System Efficiency Below Threshold Bank 2. Customers may also comment on the following: â—� Vehicle f
- TSB 26-22162026-05-06 · Power Train
- This bulletin supersedes 25-2549. Reason for update: To add 2020 model year chassis cab vehicles. Some of the vehicles listed in the Model statement above may exhibit an incorrectly illuminated malfunction indicator lamp (MIL) with diagnostic trouble codes (DTC) P0420 and/or P0430 stored in the powertrain control module (PCM). This may be due to the software in the PCM. This condition does not aff
- ATI&04132026905 Other2026-04-13 · Engine
- Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2025 Pilots with customer complaint of Check Engine Light (CEL) on with DTC P0420 [Catalyst System Efficiency Below Threshold (Bank 1)] and/or P0430 [Catalyst System Efficiency Below Threshold (Bank 2]] stored. To better understand the cause of this condition, AHM would like to collect specific parts from the vehicle.
- S26250000042026-03-31 · Electrical System
- Active/Pending Diagnostic Trouble Code (DTC) P24A0, P2482, P2481, P0420, P2470, P2471, P2472, P242D, P242B, P244D, P1484 And/or P214D setting In The Powertrain Control Module (PCM)
- S26250000032026-03-31 · Electrical System
- Active/Pending Diagnostic Trouble Code (DTC) P24A0, P2482, P2481, P0420, P2470, P2471, P2472, P242D, P242B, P244D, P1484, P106D, P1060 And/or P354B Setting In The Powertrain Control Module (PCM)
What P0420 means
Source: SAE J2012 / OBD-IIThe catalytic converter on bank 1 is not cleaning up the exhaust as well as it should.
A stored code names the test that failed, never the part that caused it. It is the starting point of a diagnosis, not its conclusion — the same code has several possible causes and the cheap one is not always right.
Common questions about P0420
Source: NHTSA files and the OBD-II standardCan I keep driving with P0420 stored?
Nobody can answer that from the code alone, and a site that does is guessing. A steady light generally means the fault was logged and the vehicle is in a reduced-risk mode; a flashing light means stop soon, because a misfiring engine can destroy a catalytic converter in minutes. The safe read of this page is the mileage and the components, not permission.
Does a code mean the car is recalled?
No. Recalls are filed by campaign and matched by VIN, and none of them are triggered by a scan tool. If you want to know whether an open recall applies to one specific vehicle, check the VIN at nhtsa.gov/recalls — that is the only source that settles it.
Why do the counts here differ from other sites?
Because these are not estimates. Every number on this page is a count of documents in NHTSA's own files: manufacturer communications that name the code in their filed summary, and owner complaints that name it in the narrative. We do not model, weight or extrapolate them.
Will clearing the code fix it?
Clearing turns the light off and erases the freeze-frame data a technician would have used to work out what happened. If the condition is still there the code returns, usually within a few drive cycles, and the diagnosis now starts from less information than before.