P0304 – Misfire in cylinder 4

System: Engine - ignition
Dashboard light: Check engine light (MIL)
Check-engine blink code: —
Applies to: 1SZ-FE (by platform)
Description: Misfire in cylinder 4
Possible causes: Trouble area: 1.Spark plug 2.Ignition coil 3.Injector 4.Compression
What to check: Checking points: 1.Swap coil and plug with another cylinder 2.Check injector 3.Check compression
Confidence: medium (Toyota Echo 1999–2002 factory diagnostics, same XP10 platform; not confirmed on JDM 1SZ-FE)

From the factory service material. Clear the code and test-drive to confirm it returns. Search all fault codes · Common problems · Warning lights