P0300 Random/Multiple Cylinder Misfire Detected
The PCM has detected misfires that are not isolated to a single cylinder.
Definition
P0300 is set when the crankshaft position sensor detects engine speed irregularities consistent with misfires across multiple cylinders or no specific cylinder. If a cylinder-specific code (P0301-P0312) is also present, focus on that cylinder first.
Common causes
- Worn spark plugs or wires
- Failed ignition coil (especially coil-on-plug)
- Vacuum leak
- Low fuel pressure
- Failing crankshaft or camshaft position sensor
- EGR valve stuck open
- Low compression
Common misdiagnoses
- Replacing all coils when only one is faulty (swap test the suspected coil to confirm).
- Ignoring fuel trim data — a lean misfire is a different fix than an ignition misfire.
Troubleshooting steps
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1. Read all cylinder-specific misfire codes
P0301-P0312 narrow down which cylinder(s) are misfiring.
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2. Check spark plug condition
Pull plugs and inspect for fouling, gap, or damage.
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3. Swap coils between cylinders
If a misfire follows the swapped coil, that coil is bad.
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4. Check fuel trim and pressure
Lean misfires need different fixes than spark/coil problems.
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5. Test compression
Low compression on one or more cylinders indicates mechanical engine issues.