For the most accurate technical data, official Toyota portals are the primary choice:

There are several sources where you can find a Toyota Avanza service manual PDF download. Here are some options:

If you truly need a (not just an owner's manual) for repairs like timing chain replacement, automatic transmission overhaul, or ABS diagnostics, the best option by a huge margin is:

A high-quality service manual should include detailed information on: Toyota Avanza Owners Manual