P0420 The catalytic converter on bank 1 is not cleaning up the exhaust as well as it should
117 owner reports and 553 manufacturer filings across 199 model years from Acura, Buick, Cadillac, Chevrolet and others.
Where P0420 shows up
Source: NHTSA manufacturer communications and complaintsShowing the 25 model years where P0420 appears most; it is on file for 199 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.
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P0420 by make
The same record, one make at a time: the model years, bulletins and owner reports that name P0420 on that maker’s vehicles.
What it gets filed under
When owners report it
miles, typically
Half of the 19 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.
The vehicle has had a chronic, active P0420 Catalytic Converter efficiency code caused by a known Kia manufacturing defect of massive, excessive oil consumption (requiring constant oil additions to maintain operation)
The vehicle presented with an active check engine light for diagnostic trouble code P0420 (Catalyst System Efficiency Below Threshold)
The check-engine light is on and the vehicle has produced diagnostic trouble codes P0420 and P0430, indicating catalyst-system efficiency problems affecting both banks
Vehicle Details: 2020 Kia Soul, 2.0L Nu MPI Engine Complaint Description: My vehicle is experiencing severe, excessive engine oil consumption at 99,000 miles, which has directly resulted in a P0420 diagnostic trouble code (Catalyst System…
The contact associated the failure with Technical Service Bulletin: 21-010 (Warranty Extension: MIL Comes On with DTC P0420, P0430, P030x, and P219A/B (Without Software Update); however, the vehicle was not covered under the TSB
553 manufacturer filings name P0420. Start with what the maker wrote down.
A code names the test that failed, not the part. A bulletin that names it is often a diagnosis someone has already written down — quote its number at the service desk.
Manufacturer filings that name it
Source: NHTSA manufacturer communicationsService bulletins and campaigns whose filed summary names P0420.
- 18-073-26 Service bulletin2026-07-22 · Power Train
- 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): ● P0420 - Catalyst System Efficiency Below Threshold Bank 1. ● P0430 - Catalyst System Efficiency Below Threshold Bank 2. ● P0556 - Brake Booster Pressure Sensor Circuit Performanc
- 18-063-26 Service bulletin2026-06-25 · 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): ● P0420 - Catalyst System Efficiency Below Threshold Bank 1. ● P0430 - Catalyst System Efficiency Below Threshold Bank 2. Customers may also comment on the following: ● Vehicle fails e
- TSB 26-2216 Service bulletin2026-05-06 · 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.
- S2625000004 Service bulletin2026-03-31 · 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)
- S2625000003 Service bulletin2026-03-31 · 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 means a fault was logged and the car should be checked soon; a flashing light means a severe misfire — slow down and get it seen as soon as possible, because severe misfire can quickly damage the catalytic converter. 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.