A P0303 diagnostic code on your 2020 Lexus IS indicates the engine control module has detected repeated misfires in cylinder 3. The sport sedan offers turbocharged and naturally aspirated V6 powertrains.
2020 IS Engine Options
The 2020 IS 300 (RWD) uses a 2.0L turbocharged four-cylinder, while the IS 300 (AWD) and IS 350 use the 3.5L V6. On the inline-4, cylinder 3 is third from the front. On the V6, cylinder 3 is at the rear of the left bank.
Common Causes
- Ignition Coil Failure: Both engines use coil-on-plug ignition
- Spark Plug Wear: Turbo engines may need earlier plug attention
- Boost System Issues: IS 300 turbo sensitive to intake leaks
- Fuel Injector Problems: Direct injection deposits or failures
- Carbon Buildup: GDI technology contributes to valve deposits
Diagnostic Approach
Identify your engine type first. Use Lexus diagnostic equipment for detailed access. Monitor boost pressure on turbo models. Test ignition components through swap testing.
Repair Solutions
Replace failed ignition coils with Denso OEM parts. Install properly specified spark plugs for your engine type. Repair boost leaks on turbo models. Address carbon buildup through professional cleaning.