When your 2023 Toyota Sienna displays the P0304 code, the powertrain control module has identified consistent misfires in cylinder 4. The 2023 Sienna continues as a hybrid-exclusive minivan.
2023 Sienna Hybrid System
The 2023 Sienna uses the 2.5L Dynamic Force four-cylinder with hybrid motors producing 245 hp combined. D-4S dual injection helps prevent carbon buildup. Cylinder 4 is the rearmost.
Typical Causes
- Ignition Coil Problems: Coil-on-plug failures
- Spark Plug Condition: D-4S specific requirements
- Fuel Injector Issues: Dual injection system
- Hybrid Operation: Engine cycling
- Carbon Accumulation: Less common with D-4S
Diagnostic Process
Use Toyota hybrid diagnostics. Ensure engine is running during testing. D-4S helps prevent carbon. Test ignition components systematically.
Repair Recommendations
Replace faulty ignition coils with Denso parts. Install properly specified spark plugs. D-4S system is reliable.