OBD2 Code P0300: Random/Multiple Cylinder Misfire Detected
The P0300 code means Random/Multiple Cylinder Misfire Detected. Estimated repair cost: $150 – $1200.
📋 Diagnostic Reference
| OBD2 Code | P0300 |
| Category | Powertrain |
| Severity | Check Soon |
| Repair Cost | $150 – $1200 |
| Can You Drive? | ⛔ STOP NOW if flashing / ⚠️ Diagnose soon if steady |
🔍 Symptoms
- Engine shaking/rough idle
- hesitation on acceleration
- check engine light flashing (STOP immediately if flashing)
- fuel smell from exhaust
- hard starting
⚠️ Most Likely Causes (in order of probability)
- Worn spark plugs
- faulty ignition coils
- vacuum leak
- clogged fuel injectors
- low fuel pressure
- EGR valve stuck open
- timing chain/belt issue
🛠️ Diagnostic Procedure
Step 1: If Check Engine Light is FLASHING stop driving immediately — catalytic converter...
If Check Engine Light is FLASHING stop driving immediately — catalytic converter damage is occurring
Step 2: Scan for cylinder-specific codes (P0301-P0308) to narrow down
Scan for cylinder-specific codes (P0301-P0308) to narrow down
Step 3: Remove and inspect spark plugs — look for fouling oil or wear patterns
Remove and inspect spark plugs — look for fouling oil or wear patterns
Step 4: Swap ignition coils between cylinders to isolate a bad coil
Swap ignition coils between cylinders to isolate a bad coil
Step 5: Smoke test intake for vacuum leaks
Smoke test intake for vacuum leaks
Step 6: Compression test if plugs and coils are good.
Compression test if plugs and coils are good.
🔌 Don't Pay $150 for a Code Read — Diagnose It Yourself
Dealerships charge $100-$200 just to scan your car and read the code. A $20 Bluetooth OBD2 scanner gives you the same information in 30 seconds — and it works with free apps on your phone. Read and clear codes yourself before deciding if you need a mechanic.
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