A bi-directional scan tool works by making use of specialized hardware that allows information to flow both ways between the tool and the vehicle. Because of this, the person using the tool can actually command the vehicle to perform various functions, such as opening the throttle or powering the ignition. This allows mechanics to easily run tests on their vehicles without actually having to get in the driver's seat. They can walk around the car whilst inputting commands on the bi-directional scan tool to see exactly how the vehicle systems respond. As a result, a technician can pinpoint problems and issues with a vehicle without having to use a tedious trial-and-error approach. Being able to control a vehicle's functions via an external tablet is a very powerful technique and can transform the way a workshop handles its jobs.