P0300
Random or multiple-cylinder misfire detected
Severity: Inspect soonMisfire codes
A misfire is a cylinder firing stroke that does not burn its fuel properly. The engine computer detects it from tiny changes in crankshaft speed. Misfire matters for safety and cost because unburned fuel goes into the catalytic converter and can overheat it, which is why the check engine light flashes when misfire is severe.
How these codes differ
- P0301 to P0306 name one cylinder (the last digit is the cylinder number). P0300 means misfire is spread across more than one cylinder, or the computer cannot pin it to one. The regulation requires a cylinder-specific code when the computer can identify the cylinder and a multiple-cylinder code when two or more cylinders share the misfires.
- A single-cylinder code points to something that belongs to that cylinder: its coil, spark plug, plug boot or injector, or its own compression. A random code (P0300) points more toward something all cylinders share: fuel pressure, a lean mixture, a vacuum leak, or ignition or sensor problems that affect every cylinder.
- The light's behaviour changes the urgency more than the code number does: a steady light means misfire was detected at a level that raises emissions; a flashing light means misfire is happening now at a level that can damage the catalytic converter.
Codes that show up together
- P0300 with one or more cylinder codes: start with the named cylinder(s), but check shared causes if several unrelated cylinders are listed.
- Misfire codes with lean codes (P0171, P0174): treat the lean condition first, because a lean mixture can cause misfire.
- Misfire codes with catalyst codes (P0420, P0430): fix the misfire first; repeated misfire damages the converter.
Misfire codes
P0301
Misfire detected in cylinder 1
Severity: Inspect soonP0302
Misfire detected in cylinder 2
Severity: Inspect soonP0303
Misfire detected in cylinder 3
Severity: Inspect soonP0304
Misfire detected in cylinder 4
Severity: Inspect soonP0305
Misfire detected in cylinder 5
Severity: Inspect soonP0306
Misfire detected in cylinder 6
Severity: Inspect soonP0316
A misfire was detected during the first 1,000 engine revolutions after start-up
Severity: Inspect soonP0307
Misfire detected in cylinder 7
Severity: Inspect soonP0308
Misfire detected in cylinder 8
Severity: Inspect soonP1399
On Honda and Acura, a random misfire that the computer cannot pin on one cylinder
Severity: Severity not verifiedP0309
Misfire detected in cylinder 9
Severity: Severity not verifiedP0311
Misfire detected on cylinder 11
Severity: Inspect soonP0312
Misfire detected on cylinder 12
Severity: Inspect soon
Sources and review
- Final Regulation Order: 13 CCR §1968.2, Malfunction and Diagnostic System Requirements (OBD II), 2004 and subsequent model-year passenger cars, light-duty trucks and medium-duty vehicles (2015 amendments)
- OBD consumer brochure: Do you drive a 1996 or newer car or light truck? (EPA420-F-02-016)
- 2023 Integra Owner's Manual: Indicator, Coming On/Blinking
- Diagnosing Those Maddening Misfires
- Trouble Shooter: 2002 Trooper, Hit or Miss
- How to Fix P0420 Emissions Code
- Random Misfires (OBD II P0300 DTC)
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error