TorqueMech OBD Code Guide
P0301 - Cylinder 1 Misfire Detected
The ECM detected a misfire on cylinder 1.
Severity
Medium
Drivability
Single-cylinder misfire, rough idle, reduced power
Typical Cost
$120 - $650+
Code Meaning
The ECM detected a misfire on cylinder 1.
What You May Notice
- Rough idle at stoplights
- Loss of power under load
- Engine shake or stumble on acceleration
- Flashing check engine light if the misfire is severe
Common Causes
Worn spark plug
Faulty ignition coil or plug wire
Injector issue
Compression/valve issue
Vacuum leak affecting that cylinder
Quick Checks
- Swap coil to another cylinder and see if misfire follows
- Inspect spark plug condition/gap
- Check injector connector and fuel trim
- Perform compression/leak-down if persistent
- Check for intake/vacuum leak near that runner
Cylinder 1 Ignition / Injector Path
- Check ignition coil power and ground on the affected cylinder
- Inspect injector connector fit, pin drag, and harness routing
- Verify shared engine ground integrity before replacing parts
Likely Repairs
Use test results to confirm the fault before pricing the repair.
Ignition coil replacement
Estimator-ready next step for a confirmed repair path.
Spark plug replacement
Estimator-ready next step for a confirmed repair path.
Fuel injector replacement
Estimator-ready next step for a confirmed repair path.
Vacuum leak smoke test
Estimator-ready next step for a confirmed repair path.
Related Cost Guides
Use these only when testing has already pointed you to a matching repair path.
Spark Plug Replacement Cost
A strong next cost check when the cylinder-specific misfire tracks back to the plug.
Next Steps
Move from the code to a diagnosis path, then into repair pricing once the fault is confirmed.