P0300: Random/Multiple Cylinder Misfire Detected
P0300 means Random/Multiple Cylinder Misfire Detected. The engine computer has detected misfires that are not limited to one cylinder, or that move between cylinders. It detects them by measuring small changes in crankshaft speed.
A random misfire across several cylinders points to something that affects the whole engine: fuel pressure, a vacuum leak, worn plugs or timing. Misfires limited to one cylinder usually set a cylinder-specific code (P0301–P0312) instead.
Can I keep driving? Limit driving and diagnose promptly. Continued driving can cause damage, stalling or limp mode.
Common symptoms
- Check engine light on, or flashing during misfire
- Rough idle and shaking
- Hesitation and loss of power
- Fuel smell from the exhaust
- Poor fuel economy
Possible causes
- Worn spark plugs
- Vacuum leak or lean condition affecting several cylinders
- Low fuel pressure
- Faulty ignition coils (several at once is less common)
- Contaminated or poor-quality fuel
- Low compression or engine mechanical issues
- Incorrect cam timing
How to diagnose P0300
- Check for other codes first (fuel trim, cam/crank, MAF).
- Look at the misfire counters for each cylinder on a scan tool.
- Inspect spark plugs: their condition tells a lot.
- Check fuel trims for a lean condition.
- Do a compression or leak-down test if ignition and fuel check out.
A flashing check engine light means misfires severe enough to overheat and damage the catalytic converter. Reduce load and get it checked right away.
What the code means, digit by digit
Generic codes have the same definition on every OBD-II vehicle (petrol cars from model year 1996 in the US, 2001 in the EU; diesels later). Manufacturers can add their own enhanced codes; those are not listed here.
Symptoms linked to P0300
Related codes
General guidance only. Fault codes describe what the engine computer saw, not which part failed: confirm with testing before replacing parts, and follow the vehicle's service information.