P0300
Random or multiple-cylinder misfire detected
Severity: Inspect soonCar shaking with the check engine light on
Severity: Inspect soon
Shaking with the light on usually means the engine is misfiring, which can stall the car and sends unburned fuel into the catalytic converter, so it needs diagnosing soon.
It gets more serious if:
- Stop: Stop if the check engine light is flashing: that is misfire bad enough to damage the catalytic converter. Pull over safely away from anything flammable, switch off and let it cool. If it flashes again after a restart, have the car taken in or drive gently and slowly only to the nearest repair shop as the owner's manual directs.
How to tell what's causing it
-
The check engine light is flashing while the car shakes.
The regulation requires the light to flash when misfire is severe enough to damage the converter. This is the stop case, whatever the code.
Points to: P0300, Catalytic converter
-
A scan shows one cylinder code (P0301 to P0306), and the shaking is steady or worse under load.
A cylinder-specific code points to that cylinder's own parts. On coil-on-plug engines, swapping the coil or plug and seeing whether the misfire moves is the quickest way to split them.
Points to: P0301, P0302, P0303, P0304, P0305, P0306, Ignition coil
-
A scan shows P0300 with lean codes (P0171, P0174), and the shaking is worst at idle.
A mixture lean enough can misfire on several cylinders; the lean condition is usually the thing to fix first.
Points to: P0300, P0171, P0174, Mass airflow (MAF) sensor
-
The shaking comes with hard starting or stalling and a crankshaft or camshaft sensor code.
The computer times spark and fuel from these sensors and uses crankshaft speed to detect misfire, so a faulty signal can cause both rough running and misfire.
Points to: Crankshaft position sensor, Camshaft position sensor
Codes that go with it
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 soonP0171
Engine computer has reached its limit adding fuel on bank 1: the mixture is lean
Severity: MonitorP0174
Engine computer has reached its limit adding fuel on bank 2: the mixture is lean
Severity: MonitorP0335
Crankshaft position sensor A circuit fault
Severity: Inspect soonP0340
Camshaft position sensor circuit fault (bank 1 or single sensor)
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)
- Frequently Asked Questions About On-Board Diagnostics (EPA 420-F-97-003)
- 2023 Integra Owner's Manual: Indicator, Coming On/Blinking
- 2020 Nissan Altima Owner's Manual
- Diagnosing Those Maddening Misfires
- Coil-on-plug misfire diagnostics (April 2001 issue PDF)
- Random Misfires (OBD II P0300 DTC)
- Ford P0171 & P0174 Lean Codes (Larry Carley)
- Advanced Engine Performance Specialist Test (L1) Composite Vehicle Type 4 Reference Booklet
- What are the symptoms of a bad crankshaft sensor?
- 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