Step-by-step guides
Short walkthroughs for the things people ask about most often. Every step is something the app really does.
How to find an air leak using fuel trimsOne two-minute experiment halves a dozen possible causes — and costs nothing.How to check the battery and alternator with the appThree voltage readings answer the question of who is to blame: the battery, the alternator or the wiring.How to reset the service interval after an oil changeThe order of steps, and an honest answer to why it does not work on every car.How to connect an OBD-II adapter and take the first readingsFrom the socket under the wheel to the first list of fault codes — eight steps, about ten minutes.Reading a fault code: the letter and four digitsP0171 is not a random string but an address. We take it apart, sign by sign.How to check a car before buying, in ten minutesWhat the socket shows, what it never shows — and why freshly cleared codes are visible.How to find which cylinder is misfiringTwo counters and one swap answer the question a garage charges money for.How to get ready for an emissions test in a weekThe main reason for failure is not a fault but incomplete self-tests. Nothing in the car shows them.A report for the mechanic when the fault is intermittent«Everything is fine here» is the most annoying phrase. A trip recording ends it.The code came back after a reset — what it meansClearing a code and fixing the car are different things. How to tell whether the cause is gone.How to check the catalytic converter with the oxygen sensorsBefore replacing the catalyst, look at two graphs: often it is not the guilty part.How to tell whether the thermostat is to blameWeak heater and higher fuel use? One graph answers the question in ten minutes.How to check the EGR valve with live dataJerky at mid revs and smoky — read two numbers instead of stripping the intake.Fuel use went up — where to startThree readings separate a real fault from winter and traffic.Hard to start when cold — what to look atThe check takes one morning and halves the list of suspects.Unstable idle — how to find the causeFour readings on one screen show what exactly is swinging.How to take a freeze frame and what to read in itThe table the unit saved at the moment of the fault answers half the questions.After a repair: how to be sure it is actually fixedAn empty fault list at the garage means nothing. What to check before you pay.Selling a car: what to show the buyer yourselfA report taken in front of the buyer removes half the haggling and the «what was reset» questions.Is your adapter lying: a five-minute checkA cheap clone answers briskly but cannot do half the protocols. Here is how to spot it.