When your 2022 Toyota 4Runner displays the P0305 code, your engine control module has detected repeated misfires in cylinder 5. In the 4Runner's 1GR-FE 4.0-liter V6 engine, cylinder 5 is located at the rear position of the left (passenger side) bank. This cylinder position can present unique diagnostic challenges due to reduced airflow and heat dissipation in that area of the engine bay.
Understanding Cylinder 5 Location in the 4Runner V6
Toyota's 1GR-FE V6 uses a firing order of 1-2-3-4-5-6, with cylinders 1, 3, and 5 on the passenger side bank and cylinders 2, 4, and 6 on the driver side. Cylinder 5's rear position means ignition components and the spark plug are harder to access and may experience more heat soak during extended idling or off-road use.
Common Causes of P0305 in the 2022 4Runner
Spark plug degradation is the most frequent cause, especially if the 4Runner sees regular towing or off-road duty. The variable valve timing with intelligence (VVT-i) system on this engine can also contribute to misfires if oil quality degrades or oil changes are delayed. Carbon buildup on intake valves, while less common in port-injected engines, can occur over time. Ignition coil failure at cylinder 5's coil-on-plug unit is another possibility.
Diagnostic Steps
Begin by accessing cylinder 5's spark plug to inspect for wear, fouling, or damage. Check the ignition coil for cracks or corrosion. Use a scan tool to monitor misfire counts across all cylinders to confirm the issue is isolated to cylinder 5. If mechanical concerns exist, a compression test will reveal any internal engine problems.
Repair Considerations
Replace the spark plug with an OEM-equivalent iridium plug gapped to Toyota specifications. If the ignition coil shows signs of failure, replace it. Consider performing a fuel injector cleaning service if carbon deposits are suspected. For vehicles used in demanding conditions, ensuring proper maintenance intervals is crucial for preventing recurring misfires.