How we test
Every scanner goes into real cars, module by module, before we write a word.
A scan tool review is only useful if it says what the tool did on a car like yours. So each one starts in the bay or on the driveway, not on a spec sheet.
On the car
We connect the tool to the vehicles it claims to cover that we can get our hands on, and we note the make, model and year of each one in the review. On every car we run a full system scan and record which modules the tool found and which it could not reach. Then we read and clear codes in the engine, transmission, ABS and airbag modules where the tool supports them.
Next come the service functions people actually buy these tools for: oil service reset, electronic parking brake retraction, steering angle calibration, battery registration, throttle relearn and DPF regeneration where the car has one. For bi-directional tools we run active tests, such as cycling a fan, a fuel pump or an ABS valve, because that is how you prove a fault before buying a part.
On the bench
We time boot and connection, graph live data and check how many values the tool can show at once, try the update process, and read the warranty and update terms. If a feature is listed by the maker but did not work on any car we had, we say so.
The score
Each tool gets a score out of 10, with one decimal. It weighs coverage, functions, live data, ease of use and update terms, then sets the result against the price. Scores compare tools across the whole site, so a 7.5 DIY reader and a 7.5 tablet are equally good buys for their owners, not equally powerful tools.
The rankings sort every review by that score. When a firmware update changes what a tool can do, we retest and note the change on the review.