Your mechanic will run a series of troubleshooting checks to determine what caused your P0301 code and how to fix the cylinder misfire.
Mechanics generally start troubleshooting the easiest and cheapest to fix problems before moving on to more complex repairs. Your mechanic will try to pinpoint if it’s a leaky head gasket, a burned exhaust valve, or anything else at fault.
Here’s how your mechanic will diagnose and fix the misfire code:
1. They’ll use a scan tool to collect all the error codes and freeze frame data stored by your PCM to see if you just had a random misfire.
2. Your mechanic will take your car for a test drive to see if the code returns.
3. They’ll check for a faulty spark plug or wire and replace them if necessary. Replacing old spark plugs with iridium or platinum plugs can also help reduce the misfire rate.
4. Your mechanic will check your ignition coil pack, coil pack wires, and connectors for damage and replace them if required.
Before your mechanic replaces your spark plug and spark plug wire or coil pack and coil pack wire, ask them to inspect your fuel injector wiring. Damaged fuel injector wiring could be causing the misfire in the affected cylinder, and diagnosing this first could save time.
5. Your mechanic will perform a compression test. The compression test checks if your cylinder head valves are causing low compression.
6. They’ll check your fuel pump for low fuel pressure.
7. If the engine code persists, your mechanic will check for a faulty fuel injector and replace it if necessary.
8. They’ll inspect your distributor cap and rotor button and replace them if they’re defective.
9. Fix any other related error codes.
10. If all else fails, your mechanic will check your PCM for issues or other error codes, which may require reprogramming or replacing.
Sometimes, other overlooked issues include loose-fitting electrical connectors and disconnected vacuum hoses that can trigger code P0301.