P0302 on 2016-2019 Lexus RX HYBRID: Cylinder 2 Misfire Causes and Fixes

What's Unique About the 2016-2019 Lexus RX HYBRID

For this generation of Lexus RX Hybrid (RX450h), a misfire on any cylinder is a known issue acknowledged by Lexus in Technical Service Bulletin (TSB) L-SB-0044-19. The bulletin, which covers 2016-2019 models, specifies that the fix involves replacing the faulty ignition coil and reprogramming the engine's computer (ECM) with updated calibration software to prevent future occurrences. Some earlier models in this range were also known to exhibit rough running on a cold start, which could be related to this code, as noted in TSB L-SB-0045-12 Rev.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light is on or flashing
• Rough or shaky engine idle
• Engine hesitation or stumbling during acceleration
• Reduced engine power, possibly entering "limp mode"
• Poor fuel economy
• Smell of unburned fuel from the exhaust
• Rough running on initial start-up, especially after a cold soak [Bulletin #L-SB-0045-12 Rev]

Most Likely Causes

1. Faulty Ignition Coil 🔴 High Probability Lexus has issued a Technical Service Bulletin (L-SB-0044-19) for this exact issue, identifying faulty ignition coils and an ECM software update as the definitive solution for 2016-2019 RX450h models. This is the most common point of failure for a single-cylinder misfire on this platform.
   How to confirm: Swap the ignition coil from cylinder 2 with another cylinder (e.g., cylinder 4, which is also on the front bank). Clear the codes and drive the vehicle. If the code changes to P0304, the ignition coil is confirmed to be faulty. This is the standard diagnostic procedure before replacing the part.
   Typical fix: Replace the faulty ignition coil. The original part number 90919-A2007 has been superseded by 90919-A2013. It is recommended to use the updated OEM part. Per TSB L-SB-0044-19, a dealer will also reprogram the ECM with a new calibration file, which is covered under the Federal Emission Warranty for 96 months or 80,000 miles.
   Est. part cost: $95-$135 for OEM
2. Worn or Fouled Spark Plug 🟡 Medium Probability Spark plugs are a regular maintenance item with a service interval of 60,000 to 120,000 miles. While modern iridium plugs have a long life, they can fail, become fouled by carbon, or have an incorrect gap, leading to a misfire.
   How to confirm: After ruling out the ignition coil, remove the spark plug from cylinder 2. Inspect it for wear (worn electrode), carbon buildup, oil fouling, or damage to the ceramic insulator. A healthy plug should have a light tan color.
   Typical fix: Replace the spark plug. It is recommended to replace all six spark plugs at the same time for even performance. Use only high-quality OEM-equivalent brands like Denso or NGK. The correct OEM part number is 90919-01263, which corresponds to Denso FK20HBR8. 🎬 Watch: Step-by-step spark plug replacement for the Lexus V6 engine.
   Est. part cost: $15-$25 per plug
3. Clogged or Faulty Fuel Injector ⚪ Low Probability
   How to confirm: If the ignition coil and spark plug are good, the fuel injector is the next item to check. A professional can perform a fuel injector balance test. A DIY method is to listen for a consistent clicking sound from the injector using a mechanic's stethoscope. You can also check resistance with a multimeter; the spec for the related 2GR-FE is 11.6 to 12.4 Ω at 20°C.
   Typical fix: First, try a high-quality fuel system cleaner (e.g., with PEA) as a simple first step, as a partially clogged injector can sometimes be cleaned. If that fails, replace the faulty fuel injector. This is a more involved repair than a coil or plug.
   Est. part cost: $100-$250

Rare But Worth Checking

• Low Engine Compression: This indicates a more serious internal engine problem, such as worn piston rings, a leaking head gasket, or valve issues. A compression test is needed to diagnose this. While rare on the 2GR-FXS, it's a possibility on any engine.
• Vacuum Leak: A leak in a vacuum hose or intake manifold gasket can disrupt the air-fuel mixture. However, this would typically cause random misfires (P0300) or affect multiple cylinders on one bank, rather than a single-cylinder misfire like P0302.
• Carbon Buildup on Intake Valves: The 2GR-FXS engine uses Toyota's D-4S system, which combines both port and direct injection. While port injection helps keep valves clean, heavy carbon buildup on intake valves is still a theoretical possibility that could impede airflow into cylinder 2 and cause a misfire. This is more common on direct-injection-only engines.

Diagnosis Steps

1. Read the trouble codes with an OBD-II scanner to confirm P0302 is present.
2. Identify the location of cylinder 2. On the 2GR-FXS V6 engine, the cylinders are numbered 2-4-6 on the front bank (closest to the radiator) from passenger to driver side, and 1-3-5 on the rear bank. Cylinder 2 is the front-most cylinder on the passenger side and is easily accessible.
3. Swap the ignition coil from cylinder 2 with the coil from cylinder 4. They are both on the easily accessible front bank.
4. Clear the codes using the scanner and start the engine. Let it run and drive it for a few minutes.
5. Re-scan for codes. If the code has moved to P0304 ("Cylinder 4 Misfire Detected"), the ignition coil is the problem.
6. If the code remains P0302, the issue is likely the spark plug or, less commonly, the fuel injector.
7. Inspect and replace the spark plug in cylinder 2. The correct OEM plug is Denso FK20HBR8. It is best practice to replace all six, but this requires removing the intake manifold for the rear bank.
8. If the problem persists after replacing the coil and plug, consider running a quality fuel injector cleaner through the system.
9. If the misfire continues, further diagnosis of the fuel injector, wiring harness, and engine compression is needed, which may require professional assistance.

Parts You'll Likely Need

• Ignition Coil (OEM #90919-A2013) — This is the most common failure part for a P0302 code on this vehicle, as identified in manufacturer TSB L-SB-0044-19. This is the updated part number, superseding 90919-A2007 and 90919-02280.
  Trusted brands: Lexus/Toyota (OEM), Denso
  OEM price range: $95-$135
  Aftermarket price range: $45-$110
• Iridium Spark Plug (OEM #90919-01263) — This is a standard maintenance item and the second most likely cause of a single-cylinder misfire. The corresponding Denso part is FK20HBR8.
  Trusted brands: Denso, NGK
  OEM price range: $15-$20
  Aftermarket price range: $13-$18

Related Codes That Often Appear With This One

• P0300 — If the misfire is intermittent or begins to affect other cylinders, a P0300 (Random/Multiple Cylinder Misfire) code may appear alongside P0302. This could point to a systemic issue like a vacuum leak or fuel delivery problem.
• P0301, P0303, P0304, P0305, P0306 — These codes indicate misfires on other cylinders. Seeing them with P0302 could point to a more widespread issue. However, TSB L-SB-0044-19 notes that a single faulty coil can trigger any of these codes, not just P0302.

Technical Service Bulletins (TSBs) & Recalls

• L-SB-0044-19 (Rev1): 🎬 Watch: Official TSB repair procedure for RX450h misfire codes. Addresses MIL ON with DTCs P0301-P0306 for 2016-2019 RX450h/RX450hL. Specifies replacing the faulty ignition coil and reprogramming the ECM. Lists updated part number 90919-A2013.
• L-SB-0045-12 Rev: Mentions MIL ON with misfire codes and rough running on cold start-up for 2016-2017 models.

Platform-Specific Known Issues

• Lexus issued TSB L-SB-0044-19 for 2016-2019 RX450h and 2018-2019 RX450hL models that experience a MIL ON with misfire codes (P0301-P0306). The official repair procedure is to replace the single faulty ignition coil and reprogram the ECM with an updated calibration. This repair is covered under the Federal Emission Warranty (96 months/80,000 miles).
• An earlier TSB (L-SB-0045-12 Rev) for 2010-2017 models notes that vehicles may exhibit rough running on initial start-up after a cold soak along with misfire codes.
• A ClubLexus forum member with a 2017 RX350 (same engine family) experienced a P0302 code at 80k miles shortly after a spark plug change, highlighting that even with recent service, a coil can fail.

Mechanic-Grade Diagnostic Values

• Port Fuel Injector Resistance — expected: 11.6 to 12.4 Ω at 20°C (68°F). Failure: Resistance outside of the specified range indicates a faulty injector.
• Low-Pressure Fuel System Pressure — expected: 304 to 343 kPa (44 to 50 psi). Failure: Pressure below this range could indicate a weak fuel pump, affecting the port injection side.
• Mode $06 Misfire Count — expected: Count should be zero or very close to zero.. Failure: A count significantly higher for one cylinder compared to others indicates an intermittent or developing misfire, even without a DTC.

Hidden / Shadow Codes Worth Checking

• Mode $06 Misfire Data: The ECU tracks misfire events for each cylinder even if they don't occur frequently enough to set a P030x trouble code. This data can reveal an intermittent misfire on a specific cylinder before it becomes a constant problem. (see via Use a professional scan tool or a capable consumer tool with an app (like Torque Pro) that can read Mode $06 test results. In Toyota's Techstream software, this is best viewed under the 'Monitor' screen, which shows both current misfire 'rate' and historical 'EWMA' data.)

Scan Tool Commands That Help

• Toyota Techstream: Misfire Count Data List / Monitor — Use this to view live and historical misfire counts for each cylinder. The 'Monitor' screen provides a more accurate snapshot than the live 'Data List', especially for misfires occurring under load. This helps confirm which cylinder is the source of the issue.
• Toyota Techstream: Active Test (Power Balance) — This function allows a technician to disable one fuel injector at a time while the engine is idling. A healthy cylinder will show a noticeable drop in RPM when its injector is cut off. If cutting off the injector for cylinder 2 causes little or no change in RPM, it confirms that cylinder was not contributing power, pointing to a misfire.
• Toyota Techstream: ECU Flash Reprogramming — This is a required step after replacing the faulty ignition coil, as per TSB L-SB-0044-19. The ECM must be updated with a new calibration file to prevent future misfires. This requires a Techstream tool with an active subscription and a stable power supply of 13.5V to the vehicle battery during the process.

Wiring & Ground Locations

• ECM Pins IGT1-IGT6 — At the Engine Control Module (ECM) connector. For the related 2GR-FE, Cylinder 2's signal is IGT2 at pin C55-31.. These are the ignition trigger signal pins from the ECM to each ignition coil. A technician could back-probe the IGT2 pin to check for a command signal from the ECM, helping to differentiate between a bad coil, a wiring issue, or a faulty ECM driver.
• ECM Pin IGF1 — At the Engine Control Module (ECM) connector. For the related 2GR-FE, this is pin C55-48.. This is the ignition confirmation signal. The coils send a signal back to the ECM on this wire to confirm a spark event occurred. A missing or erratic IGF signal can help the ECM detect a misfire and could be checked during advanced diagnosis.

OEM Part Supersession History

• 90919-02280, 90919-A2007 → 90919-A2013 — Updated part to address the failure pattern identified in TSB L-SB-0044-19.

Model Year Variations Within This Range

• 2016-2019: The 2GR-FXS engine in this generation of RX450h replaced the previous 2GR-FXE. The TSB L-SB-0044-19, which details the common ignition coil failure and required ECM update, applies to all model years from 2016-2019, indicating the issue was present throughout this production run.