Diagnostics basics
How often should you run diagnostics on your car?
There is no fixed interval: what matters is reading the codes when a warning light comes on or the car does something odd, and also at every service, before an inspection and before buying a used car. A device that stays in the car lets you see warnings as soon as they appear, without waiting.
Reviewed by Daniel Morales, founder of Reprorace SL, on
When is it worth it?
When a warning light comes on, even if the car drives fine: a pending code or an emissions fault warns you before the problem grows.
One or two weeks before an inspection, to leave time to repair and for the car to complete its monitors. Before a long trip, and before buying or selling a used car.
Is it needed if no light is on?
Many faults are stored without turning on the light: pending codes, faults in control units that are not about emissions or battery warnings. Reading them at every service costs little and can get ahead of a breakdown.
On diesels with a particulate filter, checking the soot load or how often it regenerates every so often helps catch a problem before its warning light comes on.
And in a fleet or a workshop?
In a fleet, continuous diagnostics let you decide before taking a vehicle off the road and plan the workshop. In a workshop, reading every control unit when each car comes in avoids surprises.
General guidance only: every manufacturer and model has its own details. Always follow your vehicle's manual and, if in doubt, ask a workshop.
Related
Related symptoms
- Engine warning light on and steady: what it means and what to do
- Particulate filter regenerating too often: causes
Learn more
See what your car is saying
The ECO-LITE stays in the OBD port: you see the codes in your account when they appear, and your workshop can review them remotely with your permission.
Presale price: €129 · US$129
Frequently asked questions
Every how many miles should I run diagnostics?
There is no official figure. Do it when there is a warning, at every service and before an inspection.
Doesn't the workshop service already include reading codes?
Many do, but not all read every control unit. Ask.
Is it worth it before buying a used car?
Yes: seeing the codes, the monitors and the mileage each control unit stores helps spot hidden problems or a recent reset.