P1DEF
0 owner reports and 12 manufacturer filings across 4 model years from Toyota.
Where P1DEF shows up
Source: NHTSA manufacturer communications and complaints| Model year | Filed under | Bulletins | Owner reports | Parts |
|---|---|---|---|---|
| 2017 Toyota Mirai | Fuel/Propulsion System | 4 | — | Fuel pump → |
| 2016 Toyota Mirai | Fuel/Propulsion System | 4 | — | Fuel pump → |
| 2019 Toyota Mirai | Electrical System | 2 | — | Battery → |
| 2018 Toyota Mirai | Electrical System | 2 | — | Battery → |
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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What it gets filed under
12 manufacturer filings name P1DEF. 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 P1DEF.
- TSB004622 Service bulletin2022-05-05 · Electrical System
- TSB: Some 2016 ? 2019 model year Mirai vehicles may exhibit a warning message, ?FC malfunction, return vehicle to dealer for service.? This message is accompanied by Diagnostic Trouble Code (DTC) P1DEF (450 FC Stack Performance). The Fuel Control Module (FCM) calibration has been revised to address this condition
- T-SB-0318-17_Rev Service bulletin2019-09-20 · Electrical System
- TSB: REVISION NOTICE September 20, 2019 Rev2: ? Applicability has been updated to include 2018 and 2019 model year Mirai vehicles. ? The Production Change Information, Parts Information, and Calibration sections have been updated. September 5, 2018 Rev1: ? The Parts Information section has been updated. Some 2016 ? 2019 model year Mirai vehicles may exhibit a warning message, "FC malfunction, re
- T-SB-0318-17-Rev Service bulletin2018-09-05 · Engine
- TSB: REVISION NOTICE September 5, 2018 Rev1: ? The Parts Information section has been updated. Any previous printed versions of this bulletin should be discarded. Some 2016 ? 2017 model year Mirai vehicles may exhibit a warning message, "FC malfunction, return vehicle to dealer for service." This message is accompanied by Diagnostic Trouble Code (DTC) P1DEF (450 FC Stack Performance). The Fuel Con
- T-SB-0318-17 Service bulletin2017-11-20 · Fuel System, Gasoline — Fuel Injection System
- TSB: Some 2016 ? 2017 model year Mirai vehicles may exhibit a warning message, "FC malfunction, return vehicle to dealer for service." This message is accompanied by Diagnostic Trouble Code (DTC) P1DEF (450 FC Stack Performance). The Fuel Control Module (FCM) calibration has been revised to address this condition.
What P1DEF means
Source: SAE J2012 / OBD-IIP1DEF 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 P1DEF
Source: NHTSA files and the OBD-II standardWhy does this page not define P1DEF?
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 P1DEF 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.