Cylinder 1 Misfire Detected
P0301 indicates that the engine control module (ECM) has detected a misfire in cylinder 1. A misfire occurs when the air-fuel mixture in the cylinder fails to ignite properly, causing a loss of power, increased emissions, and potential damage to the catalytic converter. Common causes include faulty spark plugs, ignition coils, fuel injectors, vacuum leaks, or low compression.
01. Most Common Causes
- Faulty spark plug or ignition coil on cylinder 1
- Clogged or leaking fuel injector on cylinder 1
- Vacuum leak near cylinder 1 intake
- Low compression in cylinder 1 (worn rings, valves, or head gasket)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Engine runs rough, especially at idle or under load
- Reduced power and acceleration
- Increased fuel consumption and emissions
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Inspect spark plug and ignition coil on cylinder 1; swap with another cylinder to see if misfire moves.
Step 3: Check fuel injector operation on cylinder 1 using a noid light or multimeter.
Step 4: Perform a compression test on cylinder 1 and compare to other cylinders.
Step 5: Inspect for vacuum leaks using a smoke machine or propane enrichment.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances with a misfire as it can damage the catalytic converter and other components. Short trips to a repair shop are acceptable if the engine is not overheating or severely shaking.
How much does it cost to fix?▼
The cost varies depending on the cause. Replacing a spark plug or ignition coil typically costs $50-$150 per part. Fuel injector replacement can be $150-$400. Compression repairs can be significantly more expensive.