When your Toyota Corolla makes a clicking sound when you try to start it, it can mean several different problems exist. It can be something as simple as a loose wire to something as severe as a bad engine. There are many other reasons that lie between the two extremes.
Dead or Weakened Battery
A battery that has a low charge may not provide enough power to turn the starter over. When this occurs, you will hear only the clicking of the starter engaging, but it will not turn the engine over. When this is the case, replace the battery.
A starter motor that has gone bad can make a clicking sound as it attempts to turn the engine over. What causes this problem is a bad spot in the electrical wiring inside that does not allow the motor to spin. When this is the problem, replacement or rebuilding of the starter is required.
A loose wire on either the starter or the battery does not allow the proper voltage to turn the starter motor over. When this happens, it can be simply repaired by tightening the loose wire.
A faulty engine can cause a clicking noise, as well. When an engine locks up, the starter engages and attempts to start the engine. When it hits resistance due to the engine being locked up, it makes a clicking or clunking sound. When this occurs, serious engine repairs are needed.