Short answer
What does P0300 tell you?
P0300 appears in manufacturer guidance for specific misfire-related conditions. The code alone does not identify the cause, affected cylinder, or a failed part.
A diagnostic trouble code is a recorded monitor result, not a parts diagnosis. The same code can arise in different vehicle contexts; the exact year, make, model, engine, emissions calibration, other codes, and stated symptoms may change which manufacturer information is relevant.
Selected applications
What the OEM sources actually cover
T-SB-0056-20 · 2017–2020 86 Cold-Start Misfire Context
Published scope: 2017–2020 Toyota 86 automatic-transmission vehicles built before the bulletin's listed production breakpoint, subject to its calibration and condition requirements.
Toyota describes a limited cold-start context involving MIL with P0300 and/or a cold-start misfire. The production breakpoint and calibration status must be checked against the exact vehicle; the model and code alone are not enough.
- 2017–2020 Toyota 86Automatic transmission, VIN/production breakpoint, calibration status, and stated cold-start condition must be verified in the bulletin.
SSM 52028 · 2021–2022 Mustang 5.0L DTC Context
Published scope: 2021–2022 Ford Mustang with the 5.0L engine, subject to the bulletin's listed condition and vehicle details.
Ford includes P0300 among diagnostic trouble codes in a limited bulletin for the named Mustang application. That does not establish the same condition on other Mustangs or vehicles.
- 2021–2022 Ford Mustang · 5.0L, 5.0Confirm engine, build details, and the stated condition in the bulletin.
Limits of this lookup
A scope overlap is not a fitment verdict
The site’s preliminary vehicle matcher compares entered make, model, year, and (where structured) engine text with a small, manually transcribed list of source applications. It cannot validate a VIN, production breakpoint, emissions certification, ECM calibration, complete engine configuration, or whether a bulletin remains current.
A “possible bulletin scope match” means only that the fields entered overlap a listed source scope. A mismatch is not proof that no source applies, because this reference is incomplete. Confirm the full source conditions with the manufacturer or a qualified technician.
A conservative next step
Keep the vehicle context with the code
Record the exact code, model year, make, model, engine, other stored codes, and the circumstances described in the owner’s manual. Compare those details with the linked manufacturer source before treating a bulletin as relevant. Do not share a VIN in this lookup.
If warning lights or symptoms are severe, follow the vehicle owner’s manual and seek qualified service rather than relying on an online code explanation.
Source method: source documents and their stated scopes were checked on September 28, 2026. This date records a source review; it does not mean every model configuration was independently tested or that a bulletin has not since been superseded.