The 3SZ-VE is sensitive to dirty oil. The OCV filter is a tiny mesh screen inside the cylinder head near the timing cover. Most owners think sludge kills this engine – actually, a clogged OCV filter starves the DVVT phaser. The manual shows exactly how to extract it with a pick tool.
If you can tell me the of your vehicle (e.g., 2008 Daihatsu Terios), I can help you locate the most relevant section of the manual for your specific repair. Service Manual 3sz-Ve | PDF | Motor Oil | Ignition System
Match the third colored link to the mark on the crankshaft timing gear.