The best OBD2 scanners

What we ranked these on

We have not used any of these tools. What follows is compiled from what each maker publishes, and the ranking runs on four criteria in the order they decide a purchase:

• Systems visible. Engine only, or engine plus ABS, SRS and transmission. This is the whole decision and it is the thing listings obscure most
• Published protocol support. A maker naming the five OBD2 protocols is telling you something checkable. “Works on most cars” is not
• Brand coverage for enhanced codes. Enhanced diagnostics are always brand-limited. The question is whether the maker names the brands
• Bidirectional capability. Whether the tool can command a component or only listen to it

The three tiers, and where each one stops

The middle row is the one that matters. A check-engine light is an engine code and any of these will read it. An ABS light or an airbag light lives in a different module, and reading it requires a tool that speaks to that module — which the budget reader states plainly it does not.

Why published protocols are worth something

OBD2 is a connector standard and a set of five signaling protocols underneath it: ISO15765-4 (CAN), ISO14230-4 (KWP2000), ISO9141-2, J1850 VPW and J1850 PWM. Every 1996-and- later US-market car uses one of them, and CAN has been mandatory since 2008.

BlueDriver publishes all five by name. That is a small thing and it is the kind of small thing this site weights, because a maker willing to list its protocols is a maker you can check rather than one asking you to trust a compatibility claim.

Bidirectional, and why most people do not need it

Every scanner here reads. The Innova 5610 also writes: it can command a component to actuate, so you can tell an ABS pump to cycle or an injector to fire and watch what happens.

That is the difference between diagnosing from a code and testing a hypothesis. A code tells you a circuit reported a fault; a bidirectional test tells you whether the part responds. For anyone doing their own repairs past the parts-cannon stage, it is the capability worth paying for.

It also actuates real components on a real car. That is a way to cause a problem you did not have, and it is a good reason not to buy this tier because it sounds more capable. Buy it because you intend to use it.

A screen, or your phone

BlueDriver is a dongle with no display — everything happens in a free app. That is why it can be small and why it has no subscription, and it means a flat phone is a scanner you cannot use.

A handheld with its own screen has no such dependency and works in a car park with no signal. The trade is a small screen, a short cable and working in the footwell rather than sitting in the seat with a phone.

If you go the phone route, this is one more argument for a charger that actually charges — best USB-C car chargers, and why a car's own USB port frequently is not enough is in USB-A vs USB-C in the car.

What a scanner will not do

It will not tell you what is broken. It tells you which circuit reported a fault, which is the start of a diagnosis rather than the end of one. A code for an oxygen sensor circuit very often means a wiring or vacuum problem upstream rather than a failed sensor.

Clearing a code does not fix anything either — it turns the light off until the fault recurs, and it wipes the readiness monitors an emissions test needs, which can mean failing a test for a car that would otherwise pass. Clear codes after a repair, not before a test.

Freeze frame is the underused feature: it captures the conditions at the moment the fault set — speed, load, coolant temperature — which is often more diagnostic than the code itself.

Which one to buy

• A check-engine light and nothing else: the budget reader does that job completely, with its own screen and no phone dependency
• An ABS or airbag light, and one of the 13 named brands: BlueDriver
• You do your own repairs and want to test rather than guess: the bidirectional tool
• An unusual or gray-market vehicle: check protocol and brand support specifically before buying anything

And if the fault you are chasing turns out to be a battery that will not hold charge rather than a sensor, that is a different tool — best car battery chargers. A weak battery throws surprisingly odd codes.