What do P0299 and P0300 together mean?

Treat them as two diagnostic clues, not as proof of one failed component. In a Ford 2024 system-operation document, P0299 is defined as a turbocharger/supercharger A underboost condition. A separate Ford diesel document defines P0300 as random misfire detected. Those definitions are specific to the Ford systems described; they do not establish the correct interpretation for every make, model, engine, or year. [S1] [S2]

The useful takeaway is that the codes concern different monitored conditions in those documented systems. Their appearance together does not, by itself, prove that one caused the other or identify a repair. Have the vehicle-specific service information checked before drawing conclusions.

Start with the vehicle’s year, make, model, and engine, if known. Then record the exact codes and whether each is current, pending, or stored, as reported by the scan tool. The applicable vehicle service information matters: the Ford documents describe manufacturer-specific monitoring rather than universal test instructions. [S1] [S2]

If available, record the freeze-frame information for each code. Note the date or approximate mileage when you first saw the codes, whether they appeared together, and what you observed at the time. Keep observations descriptive—for example, “both appeared after a commute”—rather than guessing at a cause. Include any other codes shown on the scan report.

Use a simple timeline and mark unknown details as unknown. Copy the codes and statuses exactly as shown, and note whether you have freeze-frame information to share. The Ford documents support recording code status and using vehicle-specific information, but they do not establish what data a scan of your vehicle will show. [S1] [S2]

Copyable note:

“Vehicle: [year] [make] [model], engine: [known engine or unknown]. Codes shown: P0299 — [status]; P0300 — [status]. Scan date/mileage: [date or approximate mileage]. Freeze-frame information: [record details, unavailable, or unknown]. First noticed: [date or unknown]. At the time: [brief observation, or ‘no change noticed’]. Other codes: [codes or none shown].”

If you later notice a change, add its date and what you observed. Keep it factual; don’t label a component as failed just because a code appeared.

Ask the shop to confirm the codes and statuses, identify the service information that applies to your exact year, make, model, and engine, and review any available freeze-frame context. You can also ask whether the two events appear related based on the vehicle-specific information and evidence, rather than assuming they share a cause.

For example: “Could you confirm what P0299 and P0300 mean for this vehicle, review when each was recorded, and explain what evidence would be needed before identifying a cause? Please let me know whether you need the scan report or more information about when the codes appeared.”

The Ford documents support the code definitions only for the systems they describe. They do not establish the cause on your vehicle, a diagnosis, or which repair—if any—is appropriate. [S1] [S2] Leave diagnosis to a qualified professional using information applicable to your vehicle.