Engine codes
P0301: cylinder 1 misfire detected
P0301 narrows a misfire down to one cylinder, cylinder 1. That is good news: the fault is local, and a simple swap test with the ignition coil often finds the cause without any parts bought.
P0301: can I drive, and what will the labor cost?
Estimated labor, replace one ignition coil
$22 to $88
| Labor time (estimate) | 0.2 to 0.8 h |
| Rate used | $110/h |
| Technician wage, United States (average) | $27.13/h |
| High: limit driving, fix within days Limit driving and avoid hard acceleration; stop if the light flashes. | |
Labor only: parts and the diagnostic fee are not included. Hours are our estimate for a typical car; book times vary by model. Wage: BLS, May 2025.
P0301 is the generic OBD-II code for "cylinder 1 misfire detected". The computer has counted enough failed combustion strokes on cylinder 1 to set a fault; codes P0302 to P0312 do the same for the other cylinders. When only one cylinder misfires, the cause is usually one of that cylinder's own parts. In order of frequency: the ignition coil that sits on top of its spark plug on most modern engines, the spark plug itself, worn or fouled, the fuel injector for that cylinder, and low compression from a valve, a ring or a head gasket. The quickest way to sort them out is to move the coil to another cylinder, clear the code and drive. If the misfire moves with it, the coil is bad; if it stays on cylinder 1, look at the plug, then the injector. The test tool on this page reads the result. Limit driving meanwhile and stop if the light flashes.
Coil swap test: does the misfire follow the coil?
Result
Coil
| What it means: The misfire moved with the coil: replace that ignition coil. |
Swap only with the engine off and the coil connectors clipped back. Read the per-cylinder misfire counters, or wait for the new P030x code, before concluding.
Codes, rules and labor data checked by Radif Partners · Editorial policy · Method and sources
P0301 at a glance
| Code | P0301 |
| Standard description | Cylinder 1 Misfire Detected |
| System | Ignition and misfire |
| Severity | High: limit driving, fix within days |
| Common symptoms | steady shake at idle, stumble when accelerating |
The swap test, step by step
- With the engine off, unplug and remove the coil on cylinder 1. Most come out with one bolt.
- Swap it with the coil from another cylinder, for example cylinder 2, and note which went where.
- Clear the code with a scanner, or let the computer re-learn, and drive under the conditions that caused the misfire.
- Read the code again. P0302 now means the coil is at fault. P0301 again means the coil is fine.
The same trick works with spark plugs, and with injectors on some engines, although moving injectors takes longer. On engines with coil packs or a distributor the logic is similar, but one part may serve two cylinders.
When it is not the ignition
If neither the coil nor the plug moves the misfire, the injector for cylinder 1 is the next suspect: a shop can test its resistance, listen to its click or swap it. Then comes a compression or leak-down test. A misfire with a sweet coolant smell or white exhaust suggests a head gasket leaking into the cylinder, which should be confirmed before any further driving.
A note on the spark plugs
When one plug is worn, the others usually are too, as they were installed together. Replacing the full set at the maker's interval costs less in the long run than chasing one cylinder after another. If misfires begin to move between cylinders, see P0300.
Likely causes of P0301, in order
| Cause | How often |
|---|---|
| Ignition coil on cylinder 1 | most frequent |
| Worn or fouled spark plug | most frequent |
| Fuel injector on cylinder 1 | frequent |
| Low compression: valve, ring or head gasket | less frequent |
| Wiring to the coil or injector | less frequent |
P0301 repairs and labor time
| Repair | Labor (estimate) | At $110/h |
|---|---|---|
| Replace one ignition coil | 0.2 to 0.8 h | $22 to $88 |
| Replace spark plugs (inline 4 cylinder) | 0.5 to 1.5 h | $55 to $165 |
| Replace one fuel injector | 1 to 3 h | $110 to $330 |