P0303 on 2013-2018 Toyota RAV4 2.5L: Cylinder 3 Misfire Causes and Fixes

What's Unique About the 2013-2018 Toyota RAV4

The 2013-2018 RAV4 (XA40 generation) uses the highly reliable 2AR-FE port-injected engine. Unlike some modern direct-injected engines, this platform is not prone to systemic issues like carbon buildup on intake valves causing misfires. Therefore, a P0303 code is almost always caused by a simple, age-related failure of a maintenance item like an ignition coil or spark plug. The repair is very accessible, as all four cylinders are in a line and easy to reach at the front of the engine bay.

Symptoms You May Notice

• Rough or vibrating idle
• Hesitation or stumbling during acceleration
• Reduced engine power
• Decreased fuel economy
• Solid or flashing Check Engine Light
• Noticeable smell of fuel from the exhaust

Most Likely Causes

1. Faulty Ignition Coil 🔴 High Probability Ignition coils are wear-and-tear components that fail over time due to heat cycles. It's the most common reason for a single-cylinder misfire on this engine as it ages.
   How to confirm: Swap the ignition coil from cylinder 3 with another cylinder (e.g., cylinder 2 or 4). Clear the codes and run the engine. If the code changes to P0302 or P0304, the coil is definitively bad. This is a free, 10-minute diagnostic test.
   Typical fix: Replace the faulty ignition coil. It is held on by a single 10mm bolt. 🎬 Watch this quick walkthrough on replacing your ignition coils. While you can replace just one, many owners and technicians recommend replacing all four coils at the same time if they are original and the vehicle has high mileage, as the others may fail soon.
   Est. part cost: $40-$150
2. Worn or Fouled Spark Plug 🟡 Medium Probability The original iridium spark plugs have a long service life (up to 120,000 miles), but they will eventually wear out, causing a weak or inconsistent spark. An oil leak from the valve cover gasket can also foul the plug, causing a misfire.
   How to confirm: After confirming the ignition coil is good, remove the spark plug from cylinder 3. Inspect it for wear (rounded electrode), heavy carbon fouling, oil contamination, or a cracked ceramic insulator. Compare it to a plug from a healthy cylinder.
   Typical fix: Replace the spark plug. It is highly recommended to replace all four spark plugs as a set with high-quality Iridium plugs (e.g., Denso or NGK) to maintain even performance. Use a 5/8" spark plug so 🎬 See how to properly replace the spark plugs yourself.cket.
   Est. part cost: $10-$25 per plug
3. Faulty Fuel Injector ⚪ Low Probability
   How to confirm: If the coil and plug are good, the injector is the next suspect. A DIY method is to use a mechanic's stethoscope or a long screwdriver to listen for the injector's 'clicking' sound and compare it to the other cylinders. If cylinder 3's injector is silent or sounds different, it may be faulty. A professional can perform a fuel injector balance test to confirm flow rate.
   Typical fix: Replace the fuel injector for cylinder 3. This is a more involved job than a coil or plug replacement as it involves depressurizing the fuel rail.
   Est. part cost: $50-$150

Rare But Worth Checking

• Vacuum Leak: A vacuum leak near the intake manifold runner for cylinder 3 could lean out the air/fuel mixture for that cylinder only, causing a misfire. This is less common than ignition parts failure.
• Low Engine Compression: In very rare cases on this reliable engine, an internal mechanical issue like a burnt valve, worn piston rings, or a head gasket leak could cause a persistent misfire that isn't resolved by replacing ignition or fuel components. This requires a compression test to diagnose.
• Wiring Harness Issue: Damage to the wiring or connector for the ignition coil or fuel injector on cylinder 3 can cause an intermittent connection and misfires. This can be from rodent damage or chafing over time.

Diagnosis Steps

1. Read the code with an OBD-II scanner to confirm P0303 is the primary code. 🎬 Watch this video to understand what a P0303 code means. Note any other codes present.
2. Identify cylinder 3. On the 2AR-FE engine, the cylinders are numbered 1-2-3-4, counting from the passenger side (serpentine belt side) to the driver side (transaxle side). Cylinder 3 is the third one from the right when facing the engine.
3. Perform an ignition coil swap. Turn off the engine. Disconnect the electrical connector and remove the 10mm bolt holding the ignition coil on cylinder 3. Do the same for an adjacent cylinder (e.g., cylinder 2). Swap the coils between these two cylinders.
4. Reinstall the bolts and connectors. Clear the codes with your scanner and start the engine. Let it idle or drive for a few minutes until the Check Engine Light returns.
5. Re-scan for codes. If the code is now P0302, the ignition coil you moved is faulty and needs to be replaced. If the code is still P0303, the coil is likely good.
6. If the code remains P0303, inspect the spark plug. Remove the plug from cylinder 3. Check for a worn electrode, carbon/oil fouling, or physical damage. If it looks worn or fouled, replace all four spark plugs as a set.
7. If the misfire still stays on cylinder 3 after confirming the coil and plug are good, the issue is likely with the fuel injector, its wiring, or, in rare cases, a mechanical compression problem in that cylinder.

Parts You'll Likely Need

• Ignition Coil (OEM #90919-A2005 (or superseded by 90919-02258)) — This is the most common failure part for a single-cylinder misfire on the 2AR-FE engine.
  Trusted brands: Denso (OEM), NGK, Delphi
  OEM price range: $90-$130
  Aftermarket price range: $40-$90
• Iridium Spark Plug (OEM #90919-01233 (Denso SK16HR11)) — As a primary ignition component, spark plugs are a common wear item and the second most likely cause of a misfire. The OEM-equivalent NGK part is ILKAR7B11.
  Trusted brands: Denso (OEM), NGK
  OEM price range: $15-$25 per plug
  Aftermarket price range: $10-$18 per plug

Related Codes That Often Appear With This One

• P0300 — If the misfire becomes more widespread or is intermittent across cylinders, a 'Random/Multiple Cylinder Misfire' code may appear alongside P0303.
• P0301, P0302, P0304 — If other cylinders are also beginning to have issues, or if you perform a diagnostic swap of a component, the code may move to another cylinder, confirming the faulty part.

Technical Service Bulletins (TSBs) & Recalls

• T-SB-0041-13: Addresses a brief engine knock or rattle at cold startup on 2009-2012 RAV4s with the 2AR-FE engine, related to the VVT gear assembly. While not a direct cause of P0303, it is relevant to the engine's overall health and potential noises.
• T-SB-0012-11: For 2009-2010 RAV4s (and other models), this TSB addresses a rattle noise and/or MIL 'ON' with codes P0015 or P0017, related to the camshaft timing exhaust gear.
• T-SB-0148-19: While issued for the Highlander, this manufacturer bulletin notes that a P0303 code may occur in conjunction with other misfire codes (P0301-P0306).
• T-SB-0116-15 Rev: This bulletin for the Prius V notes that vehicles may exhibit a "runs rough" condition with DTCs P0300, P0301, P0302, P0303, and P0304 during light acceleration while the EGR system is active, requiring an intake manifold replacement.
• T-SB-0147-16: A manufacturer service bulletin for the Prius describes a rough idle and tapping noise at cold start accompanied by misfire codes including P0303, which was addressed by modifying the ECM logic.

Platform-Specific Known Issues

• Real-World Example: Coil Swap Confirms Failure: On the RAV4World forums, a user with a 2014 RAV4 reported a P0303 code and rough idle. Following advice from the community, they swapped the ignition coil from cylinder 3 to cylinder 1. After clearing the codes and restarting the engine, a new code, P0301, appeared. This confirmed the ignition coil was the culprit, and replacing it resolved the issue. This is a classic, effective diagnostic story for this platform.

Mechanic-Grade Diagnostic Values

• Fuel Injector Resistance — expected: 11.6 to 12.4 Ω at 20°C (68°F). Failure: Resistance outside of this range indicates a faulty injector.
• Fuel Pressure at Idle — expected: 304 to 343 kPa (44 to 50 psi). Failure: Pressure outside this range may indicate a faulty fuel pump or injectors.
• Ignition Coil Primary Resistance (Cold) — expected: 0.36 - 0.55 Ω. Failure: A reading of 0 or infinity (OL) suggests a bad coil.
• Ignition Coil Secondary Resistance (Cold) — expected: 9.0 - 15.4 kΩ. Failure: A reading outside this range suggests a bad coil.
• Ignition Coil Connector Voltage (Pin 4 to Ground) — expected: 12-14V with ignition ON. Failure: No voltage indicates an issue with the EFI relay, fuse, or wiring harness.
• Ignition Coil Ground Continuity (Pin 3 to Chassis Ground) — expected: 0-1 Ω. Failure: High resistance indicates a poor ground connection.

Hidden / Shadow Codes Worth Checking

• Mode $06, Test ID $53: This is not a DTC, but a function within advanced scan tools. It provides access to the raw misfire counts for each individual cylinder as monitored by the ECU, even before the counts are high enough to trigger a P0303 code. This is extremely useful for diagnosing intermittent misfires. (see via An advanced OBD-II scanner or Toyota's Techstream software that can access Mode $06 diagnostic data.)

Scan Tool Commands That Help

• Toyota Techstream: Power Balance Test (Active Test) — This function allows a technician to individually disable the fuel injector to each cylinder one by one. When cylinder 3 is deactivated, if there is no change in engine RPM or smoothness, it confirms that cylinder 3 was not contributing, pinpointing the misfire without swapping parts.
• Toyota Techstream: Check Compression (Active Test) — This is a relative compression test. The tool measures the amperage draw of the starter motor as it cranks the engine through each cylinder's compression stroke. A significantly lower peak for cylinder 3 would indicate a potential mechanical compression issue (e.g., bad rings, valve, or head gasket) without needing to physically remove the spark plugs for a traditional compression test initially.

Wiring & Ground Locations

• Cylinder 3 Ignition Coil Connector — On top of the valve cover, the third coil from the passenger side (belt side) of the engine.. This 4-pin connector is the direct electrical interface for the coil. A loose or corroded connection here will cause a P0303 and/or P0353. Pin 4 is 12V power, Pin 3 is ground, Pin 2 is the trigger signal (IGT) from the ECM, and Pin 1 is the confirmation signal (IGF) back to the ECM.
• Engine Ground (ME01) — A primary ground point for the ignition system is typically located on the cylinder head or engine block, often a bolt where multiple ground wires converge.. A loose or corroded main engine ground can cause intermittent and hard-to-diagnose electrical issues, including misfires on one or more cylinders. Ensuring this connection is clean and tight is a crucial step if electrical issues are suspected.
• ECM Connector A, Pin A12 (IGT3) — At the main Engine Control Module (ECM).. This specific pin sends the trigger signal *to* the cylinder 3 ignition coil. A continuity check between this pin and Pin 2 of the coil connector can rule out a broken wire in the harness.
• ECM Connector B, Pin B10 (IGF) — At the main Engine Control Module (ECM).. This pin receives the confirmation signal *from* the cylinder 3 ignition coil after it has fired. A problem on this circuit could indicate a faulty coil or wiring, even if a spark is being produced.

Real Owner Repair Stories

• YouTube Comment on 'RB The Mechanic' (2010 Toyota RAV4 4-cylinder) — P0303 code, but the problem only occurs at high speed or when climbing a hill.
  ❌ Tried (didn't work) Exchanged fuel injector from a known good cylinder, Exchanged ignition coil from a known good cylinder, Exchanged spark plug from a known good cylinder, Confirmed compression was good
  ✅ What actually fixed it The commenter did not post the final fix, but this story is valuable because it illustrates a scenario where all common component swaps fail to resolve the issue, pointing towards a more complex cause like a wiring harness issue under load, a partially clogged injector that only fails at high duty cycle, or a subtle mechanical problem.
• NHTSA ODI #11623185: An owner reported that their vehicle lost motive power and was diagnosed with DTC codes P0300, P0302, P0303, and P0304, requiring the replacement of several parts.

OEM Part Supersession History

• 90919-02252 → 90919-02258 — Standard revision and update by the manufacturer.
  Heads up: The part number 90919-02258 is often associated with 1.8L engines (like in the Corolla/Prius), while the 2AR-FE coil is 90919-A2005 or 90919-02258. There can be confusion based on where the vehicle was manufactured (Japan vs. USA). It is critical to verify the correct part number by VIN. Using the wrong coil, even if it fits, can lead to improper dwell times and eventual failure.

Model Year Variations Within This Range

• 2013-2018: While the core 2AR-FE engine remains consistent, there was a facelift in the 2016 model year. This did not significantly change the parts or procedures for a P0303 diagnosis. However, it's always best practice to confirm part numbers via VIN, especially for electronics, as mid-cycle updates to harnesses or connectors can occur. The engine itself was replaced by the A25A-FKS in the next generation starting in 2019.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Torque Converter Shudder 🔴 High — Common on 2013-2015 models. Feels like driving over rumble strips at light throttle between 25-50 mph. (Ref: TSB T-SB-0023-15 (later revised) and Warranty Enhancement Program (ZH1) were issued. The fix involves replacing the torque converter and reprogramming the ECM.)
• Infotainment System Randomly Reboots 🟡 Low — A common annoyance where the head unit gets stuck in a boot loop or freezes. (Ref: No specific TSB, but dealer software updates are available. A common DIY fix is a soft reset by holding the power knob, or temporarily disconnecting the battery.)
• Brief Engine Rattle at Cold Startup 🟠 Medium — A 1-2 second rattle immediately after a cold start, often caused by a faulty VVT gear assembly (cam phaser). (Ref: TSB T-SB-0041-13 was issued for 2009-2012 RAV4s (and other models) with the 2AR-FE engine to address this.)
• Excessive Oil Consumption 🟠 Medium — Some 2AR-FE engines can consume oil, often attributed to low-tension piston rings. The issue is exacerbated by extended 10,000-mile oil change intervals; switching to 5,000-mile intervals can help mitigate it. (Ref: No specific TSB for the 2AR-FE, but its predecessor (2AZ-FE) had a well-known warranty extension for this issue.)

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For this repair, buying a used part is generally not recommended for the core components (coil, plug, injector). The cost savings are minimal compared to the risk of receiving a part that is near the end of its service life. A used engine cover or connector pigtail from a junkyard would be acceptable.

Donor-vehicle mileage cap: roughly under 60000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For an ignition coil, check for cracks in the plastic housing or epoxy.
• Look for signs of melting or discoloration on the connector.
• Ensure the rubber boot is not torn, brittle, or swollen from oil contamination.
• Avoid parts from engines that show signs of heavy oil leaks or coolant contamination.

OEM-only on this vehicle (don't cheap out):

• While not strictly 'OEM-only', using Denso (the Original Equipment Manufacturer) for both ignition coils and spark plugs is highly recommended by Toyota specialists. Aftermarket coils, especially cheap unbranded ones, have a very high failure rate on this platform.

Aftermarket brands forum-validated for this vehicle:

• Denso (OEM)
• NGK

Brands owners have reported issues with on this vehicle:

• Unbranded, 'no-name' ignition coils and spark plugs sold on online marketplaces. These frequently cause repeat failures within a short time.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0300 — Random or multiple cylinder misfire; often appears if more than one ignition coil or spark plug is failing on the 2AR-FE engine.
• P0302 — Cylinder 2 misfire; this code often appears during the diagnostic 'coil swap' test if the faulty coil from cylinder 3 is moved to cylinder 2.
• P0301 — Cylinder 1 misfire; a companion code that may appear if the faulty coil is moved to cylinder 1 for testing, as seen in RAV4World forum reports.
• P0304 — Cylinder 4 misfire; another potential result of the code swap diagnostic test on this I4 engine.
• P0015 — Camshaft timing exhaust gear code; mentioned in TSB T-SB-0012-11 as a related MIL 'ON' condition for the AR engine family.
• P0017 — Camshaft timing exhaust gear code; associated with engine rattle and timing issues in the AR engine series per TSB T-SB-0012-11.

Frequently Asked Questions