the vitz with the 1SZ-FE or 2NZ-FE has a single-stage silent timing chain, infact ALL Z-gen engines use timing chains instead of belts as they last longer.
i'd suggest you get it inspected as soon as possible as all the vitz i have seen till now had had their milage tampered. consult your mechanic as to if it needs to be changed, but usually that shouldn't happen for at least 120-150,000 km (inspection every 60k)