OBD2 Code P0301: Cylinder 1 Misfire Detected
The P0301 code means Cylinder 1 Misfire Detected. Estimated repair cost: $80 – $1000.
✅ OK TO DRIVE (short term). Have it diagnosed at your next convenience. Monitor for new symptoms.
📋 Diagnostic Reference
| OBD2 Code | P0301 |
| Category | Powertrain |
| Severity | Check Soon |
| Repair Cost | $80 – $1000 |
| Can You Drive? | ⚠️ Yes but drive directly to a shop — limit distance |
🔍 Symptoms
- Engine vibration at idle
- power loss under load
- fuel smell
- rough running that smooths out at higher RPM
⚠️ Most Likely Causes (in order of probability)
- Faulty spark plug cylinder 1
- failed ignition coil
- fuel injector clogged or stuck
- compression loss
- vacuum leak at intake runner
🛠️ Diagnostic Procedure
Step 1: Remove spark plug from cylinder 1 and inspect — compare to other cylinders
Remove spark plug from cylinder 1 and inspect — compare to other cylinders
Step 2: Swap ignition coil with another cylinder — if misfire moves coil is bad
Swap ignition coil with another cylinder — if misfire moves coil is bad
Step 3: Check fuel injector signal with noid light
Check fuel injector signal with noid light
Step 4: Perform compression test on cylinder 1
Perform compression test on cylinder 1
Step 5: Inspect intake manifold gasket near cylinder 1 runner.
Inspect intake manifold gasket near cylinder 1 runner.
ASE Certified Review: This diagnostic guide has been reviewed by an ASE-certified master technician. Diagnostic steps follow industry best practices per SAE J1979 and OEM service procedures. Always verify with a qualified mechanic before performing repairs.
Technician's Notes: Cylinder-specific codes make diagnosis much easier. Swap components between cylinders to isolate the problem without buying parts.
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Dealerships charge $100-$200 just to scan your car and read the code. A $20 Bluetooth OBD2 scanner gives you the same information in 30 seconds — and it works with free apps on your phone. Read and clear codes yourself before deciding if you need a mechanic.
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Data Sources: Diagnostic information compiled from SAE J1979 OBD2 standards, OEM service manuals, and ASE master technician field experience. Reviewed for technical accuracy. Repair cost ranges are national estimates and vary by location. Always verify with a qualified mechanic.