P0300
OBD-II code guideRandom or multiple-cylinder misfire detected
Find out what the P0300 random misfire code means, why it matters, and what a technician should check before driving farther.
Plain-English meaning
What the signal is telling you
The engine computer has detected misfires across one or more cylinders without isolating one consistent cylinder. A misfire can affect power, fuel economy, and the catalytic converter.
Typical severity
How quickly to act
High — inspect promptly
Severity depends on how the vehicle is behaving and which other codes are present.
Likely causes
These are starting points for inspection, not an automatic parts list.
- Worn spark plugs, failing ignition coils, or damaged ignition wiring
- Fuel delivery problems such as a weak pump or restricted injector
- A vacuum leak or air/fuel mixture fault
- Low compression or an engine timing problem
Possible symptoms
Symptoms vary by vehicle and may have more than one cause.
- The engine may shake, run roughly, or hesitate.
- Starting may be difficult and power may drop.
- A flashing check-engine light can occur while a misfire is active.
Practical next steps
Give the technician useful context before replacing anything.
- 1If the check-engine light is flashing, reduce load and stop driving when safe to protect the converter.
- 2Record shaking, hard starts, stalling, or fuel smells for the technician.
- 3Request ignition, fuel, compression, and related-code checks before authorizing a parts swap.
Have this code on your dash?
Turn the signal into a useful report.
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