The 2024 Lexus RX fifth generation underwent a complete redesign, now featuring turbocharged 4-cylinder engines exclusively for North American markets. The RX 350 uses a 2.4-liter turbo-four producing 275 horsepower. When a P0305 diagnostic trouble code appears indicating a cylinder 5 misfire, this represents an anomalous diagnostic situation.
Understanding the P0305 Anomaly
The P0305 code translates to "Cylinder 5 Misfire Detected" in standard OBD-II terminology. However, the 2024 RX's turbocharged 4-cylinder engine contains only cylinders numbered 1 through 4. The appearance of this code indicates a diagnostic system irregularity.
New Generation Engine Change
Previous RX generations offered a V6 engine where cylinder 5 was legitimate. The 2024 redesign eliminated the V6 in favor of turbocharged 4-cylinder and hybrid powertrains. This significant change means P0305 is now an anomalous code on current RX models.
Diagnostic Protocol
When encountering P0305 on your 4-cylinder RX, a qualified technician should use Lexus Techstream diagnostics to verify actual misfire counter data for cylinders 1-4. Software updates and communication errors should be investigated.
Possible Causes for Erroneous Code
This anomalous code may result from ECM software requiring updates (common on redesigned vehicles), control module communication errors, or aftermarket device interference.