What does it mean?
This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to vehicles equipped with OBD-II. Although generic, specific repair steps may vary by make/model.
A P0301 code means the car’s computer has detected that one of the engine’s cylinders is not functioning properly. In this case, it’s cylinder number 1.
Symptoms may include:
- The engine may be harder to start
- The engine may stumble/misfire and/or hesitate
- Other symptoms may also be present
Causes A P0301 code can mean one or more of the following has occurred:
- Faulty spark plug or wire
- Faulty ignition coil (pack)
- Faulty oxygen sensor(s)
- Faulty fuel injector
- Burned exhaust valve
- Faulty catalytic converter(s)
- Fuel shortage
- Poor compression
- Faulty computer
Possible Solutions
If there are no symptoms, the simplest thing to do is reset the code and see if it returns.
If there are symptoms such as engine stumbling or hesitation, check all cables and connectors leading to the cylinders (i.e., spark plugs). Depending on the lifespan of ignition components in the car, it may be wise to replace them as part of your regular maintenance schedule. I suggest spark plugs, spark plug wires, distributor cap and rotor (if applicable). Otherwise, check the ignition coils (e.g., coil packs). In some cases, the catalytic converter has failed. If you smell rotten eggs from the exhaust, your catalytic converter needs replacement. I’ve also heard in other cases that the issues were faulty fuel injectors.