P0303 Code: Toyota Tacoma (2016-2023) - Causes, Symptoms & Fixes

Data note: The provided NHTSA data for Toyota Tacoma (2016-2023) shows no owner complaints for this issue and no recalls in the database. No recalls found in NHTSA database.

CODE MEANING AND SEVERITY

• Code meaning: P0303 = Cylinder 3 Misfire Detected. The PCM (engine computer) detected that cylinder 3 is not combusting as it should.
• Severity and symptoms: A single-cylinder misfire is usually less urgent than multiple misfires, but it can cause rough running, reduced power, and increased exhaust emissions. If left unresolved, persistent misfires can overheat or damage a catalytic converter and degrade fuel economy. In many cases, a P0303 is intermittent or catchable with a quick repair; in others, it signals a more serious underlying problem in the ignition/fuel system or mechanical health of that cylinder.

COMMON CAUSES ON TOYOTA TACOMA

The 2016-2023 Toyota Tacoma commonly experiences P0303 due to issues in or around cylinder 3. Typical causes include:

• Ignition system
  • Worn or fouled spark plug in cylinder 3
  • Faulty ignition coil or coil-on-plug pack feeding cylinder 3
  • Damaged coil wiring connectors or corroded terminals to the coil
• Fuel system
  • Dirty or leaking fuel injector for cylinder 3 (or injector electrical issue)
  • Clogged or stuck injector causing weak spray
• Air and vacuum system
  • Vacuum leak near cylinder 3 (intake manifold gasket, vacuum hoses, PCV routing)
  • Dirty or bent intake components affecting cylinder 3’s air supply
• Mechanical/combustion health
  • Low compression in cylinder 3 due to valve/seat leakage, worn piston rings, or head gasket concerns
  • Timing concerns from cam/ crank synchrony issues can manifest as misfires in rare cases
• Electrical/PCM
  • Wiring harness or connector problems to coil or injector for cylinder 3
  • Faulty PCM/ECU misfire detection (less common but possible after other causes are ruled out)
    Note: In many Tacomas, quick misfire fixes are often spark plug or coil-related, but it’s essential to verify with proper diagnostic steps.

SYMPTOMS

• Illumination of Check Engine Light (CEL) with P0303 stored or pending
• Rough idle or engine shake, especially at idle or during light load
• Noticeable loss of power or hesitation during acceleration
• Increased fuel consumption or rough running at certain RPMs
• In some cases, mild exhaust smell from misfiring exhaust gas
• Possible misfire transiently switching to another cylinder if ignition components move the fault

DIAGNOSTIC STEPS

A structured approach to confirm P0303 and identify root cause (for a 2016-2023 Tacoma):

• Step 1: Read codes and data

  • Use a professional-grade OBD-II scanner to confirm P0303 and check freeze frame data (RPM, load, temperature, misfire counters).
  • Check for related codes (P0300 random/multiple misfire, P0301, P0302, P0304, P0305, P0306, and fuel/oxygen sensor codes or misfire-related fuel trim codes).

• Step 2: Inspect ignition components

  • Inspect the spark plug on cylinder 3: look for fouling, worn gaps, oil/fuel fouling, cross-threading, or damaged ground strap. Replace if needed.
  • Swap test: Move the ignition coil from cylinder 3 to another cylinder (e.g., swap 3 and 1 or 3 and 2). If the misfire follows the coil (P0301 or P030? moves to the new cylinder), the coil pack is likely faulty.
  • Inspect coil connectors and wiring to cylinder 3 for damaged insulation, corrosion, or poor connection. Clean/repair as needed.

• Step 3: Inspect the fuel system

  • Check the fuel injector for cylinder 3: resistance to spec, watch for open/short; listen for clicking with a mechanic’s stethoscope; consider short-term injector test if the vehicle supports it.
  • If injector flow is suspect, perform ultrasonic cleaner service or replace the injector as needed.
  • Check for fuel trim deviations (long-term trim if available). A consistently high positive trim can indicate lean condition or a leak; a very negative trim may indicate rich condition.

• Step 4: Check for air leaks and intake conditions

  • Inspect for vacuum leaks near cylinder 3 (intake manifold gaskets, PCV hoses, throttle body seals). A smoke test is ideal to reveal small leaks.
  • Inspect intake manifolds and gaskets for cracks or loose connections around the runner to cylinder 3.

• Step 5: Check compression and mechanical health

  • Perform a compression test on all cylinders, focusing on cylinder 3. Low compression on 3 suggests mechanical issues (valve seal, ring, head gasket, or valve seating problem).
  • If compression is low, consider leak-down testing to determine exact location (valve/seat vs. piston/ring).

• Step 6: Check supporting systems

  • Inspect the crankcase ventilation (PCV valve/ hoses) and ensure there is no vacuum interaction causing misfire-like symptoms.
  • Inspect electrical connectors and grounds to the PCM that could affect a single cylinder misfire.

• Step 7: Recheck and validate

  • After performing the above repairs, clear codes, then run the engine and drive under typical conditions to verify P0303 does not reappear.
  • If P0303 reappears, revisit each system (ignition, fuel, air, compression) and consider more advanced diagnostics or professional help.

RELATED CODES

• P0300: Random/Multiple Misfires
• P0301: Cylinder 1 Misfire Detected
• P0302: Cylinder 2 Misfire Detected
• P0304: Cylinder 4 Misfire Detected
• P0305: Cylinder 5 Misfire Detected
• P0306: Cylinder 6 Misfire Detected
• Other related codes that could accompany misfires (check engine light): P030x family (misfire), P0171/P0174 (fuel trim issues), P030x with pending codes, P1351 or ignition-related codes depending on the engine family and calibration.

REPAIR OPTIONS AND COSTS (2025 PRICES)

Note: Prices vary by region, shop rate, and exact engine variant in the Tacoma. The figures below are typical ranges you might expect for 2025. Always confirm with your mechanic for a precise quote.

• Spark plug replacement (cylinder 3 only)

  • Parts: $10–$25 (OEM or equivalent)
  • Labor: $60–$120
  • Total typical range: $70–$150
  • If replacing all plugs on a 6-cylinder engine: $250–$450 (labor dominates)

• Ignition coil replacement (cylinder 3)

  • Parts (coil pack): $50–$150
  • Labor: $50–$100
  • Total typical range: $100–$250
  • Note: If you swap coils for diagnostic purposes, you may avoid unnecessary coil replacement.

• Fuel injector service/replacement (cylinder 3)

  • Injector cleaning (ultrasonic/solvent): $80–$150
  • Injector replacement (single): $120–$350 (parts) + $50–$150 (labor)
  • Total typical range: $200–$500 (for a single injector replacement with labor)

• Vacuum leak repair (lines, gaskets, PCV)

  • Small hose/gasket replacement: $60–$180 (parts + labor)
  • Smoke test plus leak repair: $100–$300

• Compression test / leak-down test

  • Services/labor: $100–$200
  • If mechanical repair is needed (valve seals, piston rings, head gasket): $1,000–$4,000+ depending on extent

• Mechanical/valve issues (head gasket, valve job)

  • Very variable: typically $1,500–$4,000+ depending on extent and whether head work is needed

• PCM/ECU related misfire (rare)

  • PCM replacement/reflash: $400–$1,200 (plus diagnostic time)

• Miscellaneous

  • Wiring harness repair or connector replacement: $50–$250 (parts) + labor

Note: If multiple cylinders begin to misfire or if the misfire persists after basic ignition and fuel work, engine mechanical issues become more likely and repairs become significantly more expensive.

DIY vs PROFESSIONAL

• Do-it-yourself options

  • Basic diagnostic steps you can perform safely: check/replace cylinder 3 spark plug, swap coil with another cylinder to test if the misfire moves, inspect obvious vacuum hoses for cracks, remove and visually inspect injector connector, and perform a simple compression check if you have the tools.
  • Pros: Lower cost, quick iteration on common issues (plug/coil).
  • Cons: Difficult access to spark plugs/coils in some Tacoma configurations; risk of misdiagnosis if you don’t test ignition, fuel, and compression comprehensively.

• When to go to a professional

  • If the misfire persists after replacing the spark plug or coil, or if compression testing reveals abnormal results.
  • If you don’t have safe smoke testing tools to check vacuum leaks, or if you’re not confident with diagnosing fuel injector circuits.
  • If you suspect a mechanical issue (low compression, valve seating problems, or head gasket failure), a professional diagnostic is recommended.
  • A professional can also perform advanced diagnostics (fuel trim analysis, cylinder balance tests, precise injector flow testing, and proper leak-down testing).

PREVENTION

• Regular maintenance
  • Replace spark plugs at Toyota-recommended intervals with the correct heat range and platinums/iridium if specified. Use OEM or quality aftermarket plugs.
  • Inspect and replace ignition coils if performance issues occur or if a misfire is diagnosed on a particular cylinder.
  • Follow recommended fuel system maintenance, including using high-quality fuel and occasional fuel system cleaners if advised by Toyota, but avoid frequent use of fuel additives as a substitute for mechanical repair when needed.
• Timely addressing of issues
  • Do not ignore a rough idle or a CEL; addressing misfires early reduces risk to catalytic converters and exhaust components.
• Vacuum and intake health
  • Inspect hoses and intake gaskets regularly for cracks or leaks; replace as needed.
• Electrical integrity
  • Keep connectors clean and dry; corrosion can cause intermittent misfires. Ensure grounds and sensor connectors are secure.
• Avoid harsh driving
  • Aggressive driving or sustained high-RPM operation when a misfire exists can exacerbate cylinder wear and exhaust damage.

Data limitations

• The provided data indicates no owner complaints and no recalls for the 2016-2023 Toyota Tacoma related to P0303 in the NHTSA database. No recalls found in NHTSA database.
• Because the data shows zero complaints for this exact issue combination, the diagnostic guide focuses on standard, well-supported causes and steps across typical Toyota small/mid-displacement V6 engines rather than any model-year-specific defect.
• Costs are 2025 estimates and can vary based on location, shop, and vehicle condition. If your vehicle has multiple misfire cylinders or unusual symptoms, prices and repair scope may differ.

In short

• P0303 on a 2016-2023 Toyota Tacoma generally points to ignition, fuel delivery, vacuum/air, or mechanical issues in cylinder 3. A systematic diagnostic approach—starting with spark plug and coil testing, then injector and vacuum checks, and finally compression/valve health—will identify the root cause. Depending on the cause, repairs range from inexpensive ignition or injector service to more expensive mechanical repairs. No recalls found in NHTSA database for this issue. No NHTSA complaints in the provided data for this combination. If in doubt, seek a professional diagnostic to avoid unintended secondary damage.