B12C5
8 owner reports and 18 manufacturer filings across 9 model years from Acura, Honda.
Where B12C5 shows up
Source: NHTSA manufacturer communications and complaints| Model year | Filed under | Bulletins | Owner reports |
|---|---|---|---|
| 2016 Honda Pilot | Electrical System | 2 | 3 |
| 2016 Honda HR-V | Electrical System | 2 | 2 |
| 2017 Honda HR-V | Engine And Engine Cooling | 2 | 1 |
| 2017 Honda Pilot | Electrical System | 2 | 1 |
| 2017 Honda Ridgeline | Electrical System | 2 | 1 |
| 2017 Acura NSX | Engine And Engine Cooling | 2 | — |
| 2017 Honda Fit | Electrical System | 2 | — |
| 2016 Honda Fit | Engine And Engine Cooling | 2 | — |
| 2018 Honda HR-V | Equipment Adaptive/Mobility | 2 | — |
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
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.
is fully aware of this systemic defect, having issued Technical Service Bulletin TSB 20-116 (Diagnostic Trouble Code DTC B12C5) specifically addressing ignition start/stop switch failure
Honda issued Service Bulletin 20-117 regarding a Warranty Extension for the 2016–2017 Pilot and 2017 Ridgeline addressing a Keyless Start System Error with DTC B12C5
The dealer confirmed that this was in no relation to the recent recall of the Ridgeline Keyless Start System Error with DTC B12C5 and that the Keyless System Main Control Unit failed, part number 38320-T6Z-A21
Manufacturer filings that name it
Source: NHTSA manufacturer communicationsService bulletins and campaigns whose filed summary names B12C5. Quoting the document number at a service desk is often the fastest route to a diagnosis someone has already written down.
- ONLY93021620212021-02-16 · Electrical System
- Owner Notification Letter - The vehicle may not start upon first press of the ENGINE START/STOP button. Also, the MID displays the error message KEYLESS START SYSTEM ERROR, and DTC B12C5 (Engine Start/Stop Switch Failure) is stored. American Honda is extending the warranty on the engine start/stop switch to 9 years from the original date of purchase or 125,000 miles, whichever comes first.
- ONLX8Z021620212021-02-16 · Equipment
- Owner Notification Letter - The vehicle may not start upon first press of the ENGINE START/STOP button. Also, the MID displays the error message KEYLESS START SYSTEM ERROR, and DTC B12C5 (Engine Start/Stop Switch Failure) is stored. American Honda is extending the warranty on the engine start/stop switch to 9 years from the original date of purchase or 125,000 miles, whichever comes first.
- ONLV92021620212021-02-16 · Engine And Engine Cooling
- Owner Notification Letter - The vehicle may not start upon first press of the ENGINE START/STOP button. Also, the MID displays the error message KEYLESS START SYSTEM ERROR, and DTC B12C5 (Engine Start/Stop Switch Failure) is stored. American Honda is extending the warranty on the engine start/stop switch to 9 years from the original date of purchase or 125,000 miles, whichever comes first.
- ONLV90021620212021-02-16 · Engine And Engine Cooling
- Owner Notification Letter - The vehicle may not start upon first press of the ENGINE START/STOP button. Also, the MID displays the error message KEYLESS START SYSTEM ERROR, and DTC B12C5 (Engine Start/Stop Switch Failure) is stored. American Honda is extending the warranty on the engine start/stop switch to 9 years from the original date of purchase or 125,000 miles, whichever comes first.
- B20-0502020-12-09 · Engine And Engine Cooling
- Service Bulletin - The vehicle may not start upon first press of the ENGINE START/STOP button. Also, MID displays the error message KEYLESS START SYSTEM ERROR, and DTC B12C5 (Engine Start/Stop Switch Failure) is stored. American Honda is extending the warranty for the keyless start system on these vehicles to 9 years from the original date of purchase or 125,000 miles, whichever comes first.
- A20-1172020-12-09 · Engine And Engine Cooling
- Service Bulletin - The vehicle may not start upon first press of the ENGINE START/STOP button. Also, MID displays the error message KEYLESS START SYSTEM ERROR, and DTC B12C5 (Engine Start/Stop Switch Failure) is stored. American Honda is extending the warranty for the keyless start system on these vehicles to 9 years from the original date of purchase or 125,000 miles, whichever comes first.
What B12C5 means
Source: SAE J2012 / OBD-IIB12C5 is a manufacturer-specific code: the second character is a 1, which under the OBD-II standard hands the definition to whoever built the vehicle. The same code can mean one thing on a Ford and something unrelated on a Hyundai. Any site that prints a single definition for it is guessing.
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 B12C5
Source: NHTSA files and the OBD-II standardWhy does this page not define B12C5?
Because it cannot be defined honestly. The second character of a trouble code says who owns its meaning, and a 1 or a 3 hands that to the manufacturer. Sites that print one definition for a manufacturer-specific code are showing you one automaker's meaning and hoping it is yours.
Can I keep driving with B12C5 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.