Our Pajero 4DR54 engine timing belt B breaks but the engine is works. How does this timing belt B function? What is the effect on the engine running without timing belt B

Sounds like one of your balance shalf belts is broke. If the main timing belt was broke the engine wouldnt start or run.

This part I believe is the Harmonic Balancer.

Without it your car will run but this may cuase damage.

However generally if you dont replace the belt the engine is out of balance. You will feel the engine vibrate constantly.

Hope this helps