In Car Mechanic Simulator 2015, the player works in a car workshop. After starting an assignment, a car appears in the shop together with a defect description - now it is the player's turn to find the cause and repair it. This requires dismantling parts of the car (in some cases directly and in others the connecting elements need to be removed first), repairing the damaged component(s) and putting everything back together. Sometimes the use of tools like the hoist is required.
While the game starts with relatively simple missions with a detailed step-to-step description, later the player also needs to do the diagnosis. There are a few tools available for this step: the ghost assembly mode which hides the car body for an easier few of its inside, inspection view which marks all components either red (faulty), green (in order) or white (not yet inspected) and a test drive. After that drive, the game automatically marks some components as faulty or in order. Other diagnostic tools like a manometer or an engine test block are unlocked with experience points.
Each finished job rewards money which has to be used to buy repair parts (the old ones can be either sold or used for other repairs) or as compensation for certain mistakes. Later in the game, the money can also be used to buy and restore used cars or old-timers. Those can either be sold at the car auction or used for collection purposes.