DTC code
P0301
Cylinder 1 Misfire Detected
Technical guide
Symptoms
- Rough idle
- shaking
- cylinder 1 misfire
- check engine light
Probable causes
- Cylinder 1 misfire
- faulty ignition coil COP
- worn spark plug
- bad injector
- low compression cylinder 1
- intake valve carbon buildup
Diagnostic steps
1) Swap ignition coil from cyl 1 to another - if fault moves, coil is bad. 2) Replace spark plug cyl 1. 3) Test injector. 4) Compression test cyl 1. 5) If compression low: inspect piston rings or valves.
Brand-specific notes (BMW, Toyota)
BMW · BMW-MS41-238 · E46/E39/E60/E90 · M54/N52/N54(partially verified)
Symptoms
- Rough idle
- shaking
- loss of power
- check engine light flashing
- catalytic converter damage risk
Probable causes
- Faulty ignition coil (most common on N52/N54)
- worn spark plug
- bad fuel injector
- low compression
- valve timing issue
Diagnostic steps
1) Swap ignition coil from cyl 1 to another cylinder - see if fault moves. 2) Replace spark plug on cyl 1. 3) Check injector operation. 4) Perform compression test on cyl 1. 5) Check valve timing.
Toyota · Corolla/Yaris/Avensis/RAV4 · 1ZZ-FE / 1NZ-FE / 2ZR-FE / 2GR-FE
Symptoms
- Rough idle
- shaking
- loss of power
- check engine light (may flash)
- fuel smell from exhaust
- possible catalytic converter damage if persistent
Probable causes
- Faulty ignition coil (individual coil-on-plug on modern Toyota - swap test)
- worn spark plug
- bad fuel injector
- low compression (1ZZ-FE has known piston ring/oil consumption issue causing low compression)
- intake valve carbon buildup
Diagnostic steps
1) Swap ignition coil from cylinder 1 to another - if misfire moves, replace coil. 2) Replace spark plug on cylinder 1. 3) Test injector. 4) Compression test - if low on cyl 1, engine internal inspection needed. 5) On 1ZZ-FE: check for oil consumption and carbon buildup.
Cross-checked technical synthesis (QA). It does not replace the manufacturer's procedure.
Models most reported with this code (NHTSA)
Count of distinct owner complaints mentioning the code. US data — same engines, same failures.
AI here is a librarian: this page shows only what mechanics confirmed, or says “unknown”. It never suggests a diagnosis — MECCANIC interprets the code, never your car.
0 confirmed cases on P0301
Nothing confirmed yet for this code. No guess is offered on purpose.
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