Cylinder 1 Misfire Detected
The P0301 code means the vehicle's onboard diagnostic system has detected: Cylinder 1 Misfire Detected. This is a serious severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- medium
- Estimated cost
- $8-$30 per spark plug; $30-$80 per coil; $25-$100 per injector (cleaning); $150-$400 (replacement injector)
The #1 fix for misfire codes. 15-piece set with 14mm, 16mm, 18mm magnetic sockets, T-handle extension, and spark plug gapper.
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Read and clear misfire codes. Shows which cylinder is misfiring so you know exactly what to replace.
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Common Symptoms
- Rough idle with a rhythmic shudder
- Flashing Check Engine Light under load
- Power loss on acceleration
- Smell of unburned fuel from exhaust
Probable Causes (Ranked by Likelihood)
- Fouled or worn spark plug on cylinder 1 Very High
- Faulty ignition coil on cylinder 1 High
- Clogged or failed fuel injector on cylinder 1 High
- Low compression on cylinder 1 Moderate
- Burnt or damaged valve on cylinder 1 Low
Step-by-Step Diagnostic Procedure
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Confirm cylinder 1 location in your specific engine. On most inline engines it is the cylinder nearest the accessory/drive belt. On V8s it varies by maker: on GM small-block/LS and Chrysler/Dodge HEMI the odd cylinders 1-3-5-7 are on the driver's (left) side with cylinder 1 at the front, while on Ford modular V8s (4.6L/5.4L) cylinders 1-4 are on the passenger side with cylinder 1 at the front. Always verify against your service manual before swapping parts.
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Swap the spark plug from cylinder 1 to a known-good cylinder. If the misfire follows the plug, replace all plugs.
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Swap the ignition coil from cylinder 1 with an adjacent coil. If the misfire code changes to the other cylinder number, replace the coil.
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Perform an injector balance test with a scan tool. A low or no contribution cylinder indicates a bad injector.
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Test compression on cylinder 1. Below 120 psi or more than 15% difference from other cylinders requires further investigation.
Common Fixes by Vehicle
What techs usually find when diagnosing P0301 on specific vehicles — tap your vehicle for the fix and the exact part:
2011-2020 Ford F-150 3.5L EcoBoost easy DIY
Cylinder 1 misfire on EcoBoost is usually a failed ignition coil (Motorcraft DG-549). Swap the coil from cylinder 1 to cylinder 3 -- if the misfire follows, replace the coil. If not, check for carbon buildup on the intake valve using a borescope. Direct injection engines are prone to this.
Labor: 30 min2014-2020 Chevrolet Silverado/GMC Sierra 5.3L hard DIY
Cylinder 1 is an AFM cylinder on the 5.3L V8. A collapsed AFM lifter is the most likely cause. TSB #18-NA-355. Diagnose by checking lifter preload with the valve cover off. If the lifter is collapsed, the entire set of AFM lifters should be replaced. Consider an AFM delete kit to prevent recurrence.
Labor: 6-8 hours2007-2017 Toyota Camry 2.5L easy DIY
Single-cylinder misfire on cylinder 1 is typically a bad ignition coil (Denso 673-1309). Swap coil from cylinder 1 to another cylinder to confirm. If misfire moves, replace the coil. Also replace the spark plug in that cylinder (NGK 91578). Check for oil leaks into the spark plug tube from the valve cover gasket.
Labor: 20 min2012-2019 Volkswagen Jetta/Passat 1.8T/2.0T TSI easy (coil), hard (walnut blast) DIY
VW TSI engines have carbon buildup issues on intake valves from direct injection. Cylinder 1 runs hottest and fouls first. Check ignition coil first (swap test), then borescope the intake valve. If heavily carboned, walnut blast is required. Also check the PCV valve -- VW revised the diaphragm design.
Labor: 20 min (coil), 3-4 hours (walnut blast)Frequently Asked Questions
How do I know which cylinder is cylinder 1?
On inline 4-cylinder engines, cylinder 1 is typically the frontmost cylinder (closest to the drive belt). On V6 and V8 engines the location varies by manufacturer. Always verify with a service manual or diagram before swapping components.
Will a misfire on cylinder 1 damage my engine?
A sustained misfire sends raw fuel into the exhaust, which can overheat and destroy the catalytic converter. A flashing CEL is a warning that damage is imminent. Address the misfire promptly.
Sources
This page is built from documented references. Verify against your own service info before repair work.
P0301 on Diesel, EV & Equipment
The same code ID appears across other engines and platforms. The diagnostic flow varies by manufacturer — these are the platform-specific breakdowns:
See All Codes & Fixes for Your Vehicle
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