Affected Component: Cylinder 3 Misfire Detected
System: Engine / Emissions / Control
Severity: Moderate – May affect drivability or emissions
🔍 What Does Toyota Error Code P0303 Mean?
P0303 – Cylinder 3 Misfire Detected indicates that the ECM (Engine Control Module) has identified a misfire in cylinder 3. A misfire means the air-fuel mixture in that cylinder isn’t igniting correctly, which leads to rough running, loss of power, and increased emissions. If left unresolved, it can damage the catalytic converter and reduce fuel efficiency significantly.
📍 When and Why It Appears
- When the air-fuel mixture in cylinder 3 fails to ignite properly
- During hard acceleration, cold starts, or idling
- ECM detects an imbalance in crankshaft speed from a misfiring cylinder
- May be triggered by a failing ignition or fuel delivery component
⚠️ Common Symptoms of P0303
- Check Engine Light ON (often flashing if severe)
- Engine shaking or vibration, especially at idle
- Poor fuel economy and performance
- Hesitation or jerking when accelerating
- Fuel smell from exhaust or rich condition
🔎 Likely Causes of Cylinder 3 Misfire
- Worn or fouled spark plug in cylinder 3
- Defective ignition coil or coil pack (coil-on-plug type)
- Fuel injector for cylinder 3 clogged or not delivering fuel
- Low compression from piston ring or valve damage
- Wiring issue or poor ground to coil/injector
- Vacuum leak near intake runner of cylinder 3
🧰 How to Diagnose Toyota Code P0303
- Use an OBD-II scanner to confirm code P0303 and freeze frame data
- Swap spark plug and coil with another cylinder—see if the code follows
- Perform a fuel injector balance test or listen for clicking from injector 3
- Use a compression tester or leak-down tester on cylinder 3
- Inspect wiring to coil and injector for corrosion or fraying
🔧 How to Fix Toyota Error Code P0303
- Replace spark plug in cylinder 3
- Replace or swap ignition coil and retest
- Clean or replace the fuel injector
- Repair damaged wiring or connectors to ignition/fuel system
- If compression is low, consult a mechanic for internal engine repair
- Clear codes and perform road test to verify fix
💰 Estimated Repair Cost (Philippines)
- Spark Plug Replacement: ₱500 – ₱1,500
- Ignition Coil Replacement: ₱1,500 – ₱3,000
- Fuel Injector Cleaning/Replacement: ₱1,000 – ₱3,000
- Diagnostics and Scan Testing: ₱800 – ₱1,500
💡 Expert Tips
- Always replace spark plugs as a set to maintain performance balance
- If misfire is intermittent, monitor live data for misfire counters
- Check engine mounts too—excessive vibration may confuse diagnosis
❓ FAQ – Toyota P0303
Can I drive with a P0303 code?
Driving short distances is possible, but prolonged driving can damage your catalytic converter and worsen engine performance.
Can I clear the code and ignore it?
Clearing the code won’t fix the underlying issue. If the misfire continues, the code will return.
Does this mean the engine is failing?
Not necessarily. Most P0303 codes are caused by ignition or fuel issues, not internal engine damage—though that should still be checked.