I can't start the engine in 20 Celsius, the battery is in a good condition I think there is something messed up with temperature sensor, cause it won't simply start when there is no sun. So how can I replace it and where it's located exactly. Any help please ?

 

There is nothing with the ambient light sensor that would affect starting (just sets the interior panel lights intensity) and the temp sensor would still allow the car to start.

Can you give us some more info? Does the ready light come on? Do you have a check engine light? Do the brake lights work (checking the brake light activation circuit)?

Do you have a friend with a good DVM and a good scanner?