Technical Description
Random/Multiple Cylinder Misfire Detected
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code. It is considered generic because it applies to all makes and models of vehicles (1996-newer), although specific repair steps may be slightly different depending on the model. So this engine code article applies to Chevrolet, Ford, Nissan, Toyota, Dodge, Honda, GMC, etc.
Basically this P0300 code means that the the car's computer has detected that not allof the engine's cylinders are firing properly.
A P0300 diagnostic code indicates a random or multiple misfire. If the last digitis a number other than zero, it corresponds to the cylinder number that is misfiring.A P0302 code, for example, would tell you cylinder number two is misfiring.Unfortunately, a P0300 doesn't tell you specifically which cylinder(s) is/aremis-firing, nor why.
Symptoms
Symptoms may include:
- the engine may be harder to start
- the engine may stumble / stumble, and/or hesitate
- other symptoms may also be present
Causes
A code P0300 may mean that one or more of the following has happened:
- Faulty spark plugs or wires
- Faulty coil (pack)
- Faulty oxygen sensor(s)
- Faulty fuel injector(s)
- Burned exhaust valve
- Faulty catalytic converter(s)
- Stuck/blocked/leaking EGR valve / passages
- Faulty camshaft position sensor
- Defective computer
Possible Solutions
If there are no symptoms, the simplest thing to do is to reset the code andsee if it comes back.
If there are symptoms such as the engine is stumbling or hesitating, checkall wiring and connectors that lead to the cylinders (i.e. spark plugs). Dependingon how long the ignition components have been in the car, it may be a goodidea to replace them as part of your regular maintenance schedule. I wouldsuggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable).Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalyticconverter has gone bad. If you smell rotten eggs in the exhaust, your cat converterneeds to be replaced. I've also heard in other cases the problems were faultyfuel injectors.
Random misfires that jump around from one cylinder to another (read: P030xcodes) also will set a P0300 code. The underlying cause is oftena lean fuelcondition,which may be due to a vacuum leak in the intake manifold or unmetered air gettingpast the airflow sensor, or an EGR valve that is stuck open.
It is helpful to have access to a factory service manual and an advanced scan tool to properly diagnose a random misfire DTC.
P0300 Diagnostics Video
Here is a helpful video that may assist you in learning more, diagnosing, and repairing your P0300 DTC. This video is intended for auto repair professionals but could be helpful to DIYers. It shows use of an advanced OBD-II scan tool during diagnostic steps:
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