The P0301 is one of several misfire codes you can read on your scan tool. I studied 120+ different vehicles with misfires and how were they fixed, to provide you with a list of the most common causes, also with an action plan to diagnose this fault in no time.
You don’t want to delay fixing your P0301 as the misfire will damage your catalytic converters or engine internals. Both of these fixes are priced at thousands of dollars while the misfire is often caused by a worn-out $5 spark plug. Fix it ASAP.
P0301 quick overview
| Meaning | P0301: Cylinder #1 Misfire Detected |
| Is it serious? | Yes, this code is serious and should be addressed immediately to prevent further damage to the engine or catalytic converter. |
| Possible causes | -Worn or faulty spark plug in cylinder #1 -Defective ignition coil for cylinder #1 -Malfunctioning fuel injector for cylinder #1 -Timing issues (e.g., incorrect valve timing) -Vacuum leak affecting cylinder #1 -Internal engine issues (e.g., valve problems or damaged head gasket) -Wiring or electrical connection problems related to cylinder #1 |
| How to diagnose? | Inspect Spark Plug: Check the spark plug in cylinder #1 for signs of wear or fouling. Test Ignition Coil: Swap the ignition coil with another cylinder to see if the misfire moves. Check Fuel Injector: Perform a swap or test of the fuel injector in cylinder #1 to confirm it’s functioning correctly. Inspect Vacuum System: Check for vacuum leaks, particularly around the intake manifold and PCV valve. Perform Compression Test: Conduct a compression test on cylinder #1 to rule out internal mechanical issues. Inspect Timing Components: Examine the timing belt or chain and related components for misalignment or damage. Inspect Wiring: Examine wiring and connections related to cylinder #1 for any faults or loose connections. |
P0301 Meaning
The P0301 code shows that your car’s engine isn’t burning fuel properly in cylinder #1. This can cause the engine to run poorly and might lead to more expensive damage if not fixed soon. Start by checking the spark plug, ignition coil, and fuel injector in that cylinder.
Diagnostics Introduction!
- Automotive electrical basics
- OBD-II scanner basics
- Using cheap tools to diagnose faults
- Bi-directional scan tool introduction
- OBD-II scanner Buyer’s Guide
Case study: real cases of solving P0301
I checked specifically for code P0301 and picked these 5 example fixes from my full case study of 123 vehicles with misfires.
How to fix P0301 on Chrysler
Car: 2006 Chrysler 300 2.7L
Problem: Misfire, P0301, P2302
Diagnosing: The technician tried to replace the fuel injector for cylinder #1, which didn’t help. Then he swapped the ignition coil to another cylinder and the misfire moved with the coil confirming that it causes the misfire.
Fix: New coil fixed the P301, however, it had to be changed once again for the OEM coil to solve the P2302 code.
How to fix P0301 on dodge
Car: 1996 Dodge Grand Caravan ES 3.8L
Problem: Misfire, P0301
Diagnosing: The technician changed the spark plugs and ignition coils and checked the fuel system which seemed fine all without any improvement. Changing the coils didn’t have to be done if he tried simply swapping the coils with each other. The cranking compression test was also showing good values, however, the running compression test uncovered the problem in the head.
Fix: Rebuilt engine head fixed the problem.
How to fix P0301 on Chevrolet
Car: 1997 Chevrolet C1500 5.0L
Problem: Misfire, P0301, P0300
Diagnosing: During the test drive, a slight misfire was noticed above 50mph and when downshifting into passing gear. Raising the RPM to 2500 in the park caused a momentary misfire at idle. However, no anomalies appeared on the scope. Fuel pressure, plugs, fuel filter, cap, and plug wires were checked and replaced as needed.
Fix: New valve springs fixed the problem.
How to fix P0301 on Volkswagen
Car: 2000 Volkswagen Jetta GLS 2.0L
Problem: Misfire, P1500, P0301, stalling
Diagnosing: The other code P1500 (fuel pump relay) was pointing directly to the fix, however, changing the relay triggered the check engine light which wasn’t present at the time of the diagnosis.
Fix: The technician bought another relay directly from the VW dealership which fixed both trouble codes and check engine light.
How to fix P0301 on Ford
Car: 2002 Ford E-150 Econoline 4.2L
Problem: Misfire, P0301
Diagnosing: The technician followed the repeating advice of multiple colleagues that had experiences with these codes on Ford vehicles. All suggested cleaning the EGR ports since their design can cause misfires only at one cylinder.
Fix: Cleaning these ports fixed the problem.
P0301 FAQ and conclusion:
Check the Wikipedia article on combustion engines if you are still unsure what exactly the misfire is. Understanding it will help you with your diagnosis.
The key takeaways from these cases
- Don’t change coils/spark plugs unless you confirm they are faulty (do a swap test at least)
- A lot of misfire cases are caused by internal engine damage/timing so don’t rush with replacing ignition/fuel parts without further diagnosis
- Your diagnosing is sometimes right, but only the OEM part will solve the issue
Diagnostics Introduction!
- Automotive electrical basics
- OBD-II scanner basics
- Using cheap tools to diagnose faults
- Bi-directional scan tool introduction
- OBD-II scanner Buyer’s Guide