P0303 Code: Toyota Camry (2018-2024) - Causes, Symptoms & Fixes

Recalls and data note

• No recalls found in NHTSA database for the 2018-2024 Toyota Camry (as of the data provided).
• The real-world data snippet you supplied includes one owner complaint for P0442 (EVAP small leak) on a 2019 Camry, not P0303. This guide uses general, model-relevant information for P0303 on Camry and notes data limitations where applicable.

CODE MEANING AND SEVERITY

• What P0303 means: The powertrain control module (PCM/ECM) has detected a misfire in cylinder 3 (Cyl 3) under certain operating conditions. The engine may run rough, shake, or lack smooth power.
• Severity and potential consequences:
  • Mild to moderate loss of power and rough idle in many cases.
  • If the misfire continues, unburned fuel can damage the catalytic converter and exhaust system; repeated misfires may stress engine components and reduce fuel economy.
  • In some driving conditions (e.g., under load or at highway speeds), a misfire can become more noticeable and the MIL (check engine light) may flash in severe cases.

COMMON CAUSES ON TOYOTA CAMRY (2018-2024, 4-CYLINDER and V6 variants)

Note: Cylinder numbering is per the engine design. P0303 is cylinder 3 misfire; on a 4-cylinder Camry that’s the third cylinder; on a V6, it corresponds to cylinder 3 of the six.

• Ignition system
  • Faulty ignition coil on cylinder 3 or its wiring/connector; coil-on-plug systems are common failure points.
  • Spark plug in cylinder 3 worn, fouled, gap out of spec, or damaged boot/connector.
  • Faulty coil harness or high-tension lead (where applicable) affected by heat or oil.
• Fuel system
  • Cylinder 3 fuel injector clogged, leaking, or not firing properly.
  • Low or unstable fuel pressure affecting cylinder 3 injector performance.
  • Dirty or contaminated fuel filter (older Camry configurations) or fuel pump issues impacting cylinder-specific fuel delivery.
• Air and vacuum
  • Vacuum leak near intake manifold gasket or around cylinder 3 intake runner.
  • Mass Air Flow (MAF) sensor or intake air circuit issue causing incorrect air/fuel mixture specifically noticeable in cylinder 3 under certain loads.
  • PCV system issues causing extra air leaks or oil fumigation into cylinder 3 (or overall misfire tendency).
• Mechanical (less common but possible)
  • Low compression in cylinder 3 due to valve seating issues, worn piston rings, blown head gasket, or damaged cam/valve train components.
  • Timing chain/belt issues (rare on Camry 2.5L modern engines but possible on some builds) leading to poor valve timing for cylinder 3.
• Electrical/PCM
  • Wiring harness or connector corrosion/damage to injector or coil for cylinder 3.
  • PCM/ECU fault or software/timing issues (generally uncommon).

SYMPTOMS OF P0303 IN A CAMRY

• Noticeable engine misfire: rough idle, shuddering, or intermittent stumble, especially at idle or under load.
• Reduced engine power and acceleration, sometimes accompanied by surging or hesitation.
• Increased fuel consumption and possibly dark or sooty exhaust.
• MIL (check engine light) illuminated; the code P0303 stored or pending.
• Possible odor of unburned fuel or minor engine vibration, particularly at startup or during acceleration.

DIAGNOSTIC STEPS (structured, practical approach)

Important: Start with safe diagnostics and use a proper OBD-II scanner to verify current/last-detected codes and freeze-frame data. For pre-2018-2024 Camry engines, the steps apply to both 2.5L 4-cyl and 3.5L V6 variants; cylinder numbering differs with engine choice, but the approach is similar.

Step 1 – Confirm and scope the issue

• Verify P0303 is current and not a one-time fault; note any accompanying codes (P0300 random/multiple misfire, P0301, P0302, P0304, etc.).
• Review freeze-frame data for RPM, engine load, fuel trims, and catalyst temperature at the time of misfire.

Step 2 – Basic mechanical and ignition checks

• Inspect spark plug in cylinder 3: condition, gap, fouling, proper seating, and signs of oil/fuel wash.
• Inspect ignition coil on cylinder 3 and its boot/connectors for cracks, burning, corrosion, or heat damage.
• Check coil harness connector for secure fit and corrosion; reseat connectors and inspect wiring for wear.
• If accessible, perform a quick swap test: swap the cylinder 3 spark plug and/or coil with another cylinder (e.g., cylinder 1) and recheck misfire behavior. If the misfire follows the component, you’ve identified the faulty part.

Step 3 – Fuel delivery and injector testing

• Measure resistance of the cylinder 3 injector and compare to known spec; compare with other injectors to spot anomalies.
• Listen for injector click using a mechanic’s stethoscope or test by swapping injector between cylinders (careful with drivability after swapping).
• Check fuel pressure to ensure the system maintains proper rail pressure; compare to service spec for the Camry engine variant.
• Consider a noid light test to confirm injector drivability if equipped to deliver pulse signals to injector.

Step 4 – Air and vacuum integrity

• Inspect all hoses, connections, and the intake manifold area around cylinder 3 for leaks or loose vacuum lines.
• If symptoms persist, perform a smoke test to identify concealed leaks around the intake runner or gasket associated with cylinder 3.
• Check PCV valve and related hoses for sticking or leaks.

Step 5 – Compression and mechanical condition

• Perform a compression test on cylinder 3 and compare against other cylinders; low compression indicates mechanical issues (valve sealing, rings, gasket).
• If compression is low, perform a leak-down test to identify the exact leakage path (valve, piston, head gasket).

Step 6 – Exhaust/PCM-related checks

• Ensure there’s no exhaust backpressure issue or sensor fault causing incorrect O2/AFR readings that can indirectly cause misfire perception.
• If all hardware checks out, consider ECM/PCM wiring and software updates; in rare cases, a recalibration or software update from Toyota may be indicated.

Step 7 – Verify and isolate

• Clear codes after any fixes and run a road test or another drive cycle to confirm P0303 is resolved and not accompanied by other misfire codes.
• If misfire reappears, repeat steps with different permutations (e.g., swap coil, swap injector, recheck compression) to isolate the fault.

RELATED CODES

• P0300: Random/multiple cylinder misfire detected.
• P0301: Cylinder 1 misfire.
• P0302: Cylinder 2 misfire.
• P0304: Cylinder 4 misfire.
• For Camry models with the 6-cylinder option, P0305, P0306, etc., may apply if misfires occur in other cylinders.
• Other codes to watch for that can accompany misfire: P030X family often coexists with P0171/P0174 (fuel trim issues), P0101 (MAF sensor), P0172/P0175 (fuel trim lean/rich conditions), or P0420 (catalyst efficiency). Data limitations mean you should rely on live data rather than assuming these appear in every case.

REPAIR OPTIONS AND COSTS (2025 prices)

Prices vary by region, dealer vs. independent shop, engine variant (2.5L 4-cyl vs. V6), and labor rates. The ranges below assume typical Camry 2018-2024 with a 4-cylinder engine; V6 scenarios may shift costs modestly upward for certain parts.

• Spark plug replacement (cylinder 3)

  • Parts: ~$4–$15 per plug (OEM vs. aftermarket).
  • Labor: ~$60–$140.
  • Estimated total: ~$70–$180.
  • Notes: If a plug is difficult to access or Tooling required, cost can edge higher.

• Ignition coil replacement (cylinder 3)

  • Parts: ~$60–$180 for a coil (OEM or premium aftermarket).
  • Labor: ~$40–$120.
  • Estimated total: ~$100–$300 per coil.
  • Notes: Use the same coil type across cylinders if replacing more than one coil; bond with new boots if required.

• Fuel injector service (cylinder 3)

  • Cleaning/flow testing: ~$60–$150.
  • Injector replacement (3) if needed (per injector): ~$120–$350 plus labor.
  • Estimated total for single injector replacement: ~$200–$650.

• Fuel system checks and tests

  • Fuel pressure test/diagnostic: ~$50–$150 if done at a shop.
  • If pressure is out of spec, repair could range from $150–$600 for pump, regulator, or lines depending on damage.

• Compression test / mechanical diagnosis

  • Compression test: ~$100–$200.
  • If low compression requires head work (valve job, gasket, etc.): $1,000–$3,000+ depending on extent.

• Valve train or head gasket repair (rare but possible)

  • Estimated total: $1,500–$4,000+ depending on extent and engine variant.

• PCM/ECU related fixes

  • Software update or reflash: ~$50–$150 (varies, some updates may be included with service).
  • Hardware ECU replacement: $500–$1,200 with programming, plus labor.

• General guideline

  • Most non-mechanical misfire cases in Camry (spark plug, coil, injector, small vacuum/air-leak fix) fall in the $100–$600 range depending on part and labor.
  • Mechanical valve/seat/head gasket failures or major engine repairs tend to be significantly more expensive (thousands).

DIY VS PROFESSIONAL

• Do-it-yourself (DIY) feasibility
  • Spark plugs and ignition coils: Highly feasible for a skilled DIYer with basic hand tools; this is often a first step.
  • Fuel injector swap or cleaning: Moderate to advanced; may require fuel system safety precautions (depressurizing the rail) and appropriate tools.
  • Compression and leak-down tests: Possible with the right tools (compression tester, leak-down tester) but can be challenging; accuracy matters.
  • Vacuum/SMOKE testing: Requires smoked test equipment or access to professional-grade equipment; DIY options may be limited.
• Professional recommended
  • When misfire persists after basic spark/coil/injector checks, or if compression tests indicate issues (low compression or abnormal leak-down), a professional diagnosis is advised.
  • If you observe repeated misfires or a powerful MIL and the car experiences safety concerns (poor acceleration, stalling), seek professional evaluation promptly to prevent catalyst damage and drivability issues.

PREVENTION

• Regular maintenance
  • Replace spark plugs at the manufacturer-recommended interval with OEM or equivalent high-quality plugs suitable for Camry engines.
  • Use the correct ignition coils or OEM-rated replacements when necessary and avoid mismatched components.
  • Keep ignition coil boots clean and free of oil/wear; inspect connectors for corrosion.
• Fuel system care
  • Use high-quality gasoline from reputable retailers; avoid fuel with unknown additives.
  • Periodically use a reputable fuel system cleaner if recommended by Toyota for your engine variant; follow product instructions.
• Air intake and sensors
  • Replace the air filter on schedule; ensure intake ducts are free of leaks.
  • Keep MAF and MAP sensors clean and functioning as per service intervals; address any sensor fault codes promptly.
• Vacuum and PCV system
  • Inspect PCV valve and hoses for kinks, cracks, or oil buildup; replace if necessary.
• Driving habit and monitoring
  • Avoid extended operation with misfires; if misfire codes trigger, pull over safely and address the issue to prevent catalytic damage.
  • If you drive in harsh conditions (heavy load, towing) and notice misfire symptoms, have the vehicle inspected sooner rather than later.
• Software and recalls
  • Keep the vehicle’s software updated as per Toyota recommendations; even if there are no recalls, service bulletins or software updates can improve misfire handling and fuel control.

Data limitations note

• The data you provided shows no Camry recalls for the 2018-2024 range; it includes one P0442 complaint (unrelated to P0303). This guide uses general Camry P0303 diagnostic practices and typical cost ranges without implying a known, model-wide P0303 issue in the supplied data. If you have access to manufacturer TSBs or updated factory service information for your exact VIN, incorporate those specifics, as they can influence diagnostic steps and repair actions.