Check Engine Light

If you mean the CEL is on while the engine is running then you need to use a scan tool to read the codes and determine from those what the problem actually is. Keep in mind that it is very rare that a code actually points to an actual bad part.

The mechanic doesn't know how to programme the Diagnoser kit.

If the mechanic doesn't know how to read codes even you really need to find someone that knows what there doing to work on your car.Getting the codes out of the computer is a very basic step and starting point for the check engine light being on.

Here is a link to help you see how to do it

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing