critical Severity — Powertrain OBD-II DTC

P0300 on Toyota Camry

Last reviewed: Aug 8, 2026 Last updated: Aug 8, 2026

Methodology: Reviewed against the SAE J2012 generic DTC definition and NHTSA owner-complaint patterns, then scoped to Toyota Camry context without treating complaints as confirmed diagnoses.

Sources: SAE/OBD-II definitions, manufacturer service information, and public reliability reports (including NHTSA where applicable).

SAE J2012 Diagnostic Trouble Code Definitions — Generic diagnostic trouble code definition reference for P0300.
NHTSA recalls, complaints, and manufacturer communications — Used to check public owner complaint context, recall status, and safety-related manufacturer communications by VIN or vehicle.

Limits: Guidance is informational and may not match every model-year or revision. Confirm with the official manual and diagnostics before replacing parts. For safety-critical or electrical work, use a qualified technician.

⚡ Quick Summary

Severity

critical

DIY Level

Moderate

Repair Cost

Urgency

Fix when convenient

🚨 Symptoms of P0300

▸ Warning light or diagnostic trouble code is stored

▸ Rough idle, shaking, hesitation, or flashing check engine light may occur

▸ Fuel economy may drop and catalyst damage risk can increase if the misfire is severe

▸ Vehicle may fail an emissions or safety inspection until the code is resolved and monitors reset

🔍 Common Causes of P0300

HIGH

Spark plug, ignition coil, injector, vacuum leak, compression, or fuel issue causing a misfire

MED

Wiring, connector, ground, or PCM driver issue affecting the misfire monitor

MED

Mechanical engine condition or catalyst-damaging misfire that needs prompt diagnosis

❓ Frequently Asked Questions

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Misfires O2 Sensors Catalytic Converter EVAP System VVT/Camshaft Fuel System Cooling System Throttle Knock Sensor EGR System

Disclaimer: This information is for educational purposes only. It is not intended as repair advice and we are not responsible for any actions you take on any vehicle. Always consult a qualified mechanic for diagnosis and repair. Repair costs shown are estimates and may vary by location, vehicle, and shop.