Four-System vs All-System OBD2 Scanners: What to Compare Before You Buy

Last reviewed 8 September 2026 · OBDCode UK editorial

If the jobs you actually do are engine, gearbox, ABS and airbags, a four-system scanner is enough. Pay for all-system only when the maker’s coverage list, the live tests and the update terms for your cars make the extra money worthwhile. A long feature list is not proof it will finish a named reset on your car.

What four-system and all-system actually mean on the box

Four-system, on the box, usually means engine, gearbox, ABS and airbags. That is most of what a driveway mechanic needs: read the code, look at live data, clear it after the repair.

All-system means the tool can talk to more modules if they are on the car — body, climate, steering, parking sensors, lights, that sort of thing. It does not mean every button works on every car. Year, engine, ECU and software still get a vote.

Compare coverage, live data, active tests and resets from published terms

Before you spend, ignore the brochure headline and ask four practical questions.

Can it get into the module you care about? Can it show live data from that module, or only a fault code? Can it command a fan, pump or actuator so you can see if the part actually responds? And is the exact reset you need listed for your car, not just named in a general menu?

The table below is from maker and UK shop pages checked on 8 September 2026, not from cars we plugged in. Two of the tools are sold as full-system. The other two are sold as four-system handhelds.

Product	Published coverage and functions	UK price on 8 September 2026	Published update and licence terms
Autel MaxiCOM MK808S	Autel’s coverage checker lists this model. You still have to search make, model, year and function. The UK Autel shop sells it as a full-system tablet with live data, active tests and more than 28 service functions. Check your car in that checker before you buy.	£319 (was £589 on the same UK Autel shop page).	The UK Autel shop says “1 year of unlimited free upgrades—no renewal fees”. That is sales copy. It does not say what a later UK renewal costs, or what still works after year one.
Launch X431 CRP129E	Launch’s English page for CRP 129E/X/I V3.0 is clear: engine, gearbox, ABS and SRS, plus common resets such as oil, SAS, EPB, TPMS and throttle. It does not claim all-system coverage or active tests on this model.	£207 (was £220) on a UK specialist listing that was out of stock.	The same listing says lifetime free updates and does not quote a subscription.
TOPDON ArtiDiag600S	The maker’s page says four-system: engine, gearbox, airbag/SRS and ABS, more than 80 brands, live data and nine maintenance jobs. Whether your car is in that list is another question.	£145 (was £185) on a UK specialist listing.	The maker’s page says lifetime free software updates at no extra charge.
THINKCAR ThinkDiag2	The UK THINKCAR shop sells it as full-system, with active tests and 15 maintenance functions. It also warns that the maintenance menu changes from car to car.	£119.95 (was £139.95 on the same UK shop page).	You get one year of full software and functions after activation. The page does not say the later UK renewal price, or what is left when that year ends.

If the maker will not show your car and the function you need, treat the feature list as advertising.

Ownership cost: hardware, updates and subscriptions

The box price is the easy number. The awkward ones are: how long updates are included, what renewal costs in the UK, whether basic diagnostics still work when the licence lapses, whether a brand or a gateway login is extra, and whether you also need a phone or tablet.

A cheap dongle with a one-year clock can cost more than a four-system handheld that keeps updating. Lifetime updates are only a bargain if the tool can actually get into the module you need.

When a four-system tool is enough for home repairs

If your week is engine lights, a gearbox warning, ABS and the odd airbag lamp, stay there. You do not need body-control coverage to read an EGR code.

The same goes if the jobs you repeat are oil-service lights, electronic parking brakes or a steering-angle reset — provided the coverage list names your car. “Oil reset” on the box is not the same as oil reset on a 2018 Focus.

When all-system coverage is the safer buy

Buy wider access if you look after several cars, or if the fault is clearly not engine or brakes: parking sensors, interior lights, climate, seats, steering, battery management, or a network that will not talk.

Pay the extra only when the published coverage for those modules is actually there. Otherwise you have bought a longer menu and the garage still has to finish the job.

Verdict: Buy for the work you keep doing. For most home repairs, four-system is the sensible default. Move to all-system when you can already see the extra modules, tests or resets on the coverage list for your cars — not because the box says “professional”.

Limits, safety and when to use a garage

A scanner tells you what the software can see. It does not prove a part is dead, and it does not fix a broken wire. Look at connectors, levels and the obvious mechanical stuff before you throw parts at it.

Do not clear an airbag, brake or steering warning just to get the lamp off. Stop and use a garage for high-voltage work, pyrotechnic restraints, brake hydraulics, immobilisers, coding you do not understand, or a calibration that could leave the car unsafe.

This page does not report first-party vehicle tests, VIN readings or completed scan procedures.

Public-source note (checked 8 September 2026): Prices, coverage claims and update terms above come from the manufacturer or UK shop pages for each tool on that date. They change. They are not test results from a car.

FAQ

Is an all-system scanner always better?

No. It can see more modules. That only helps if those modules are the ones you actually diagnose. For engine, gearbox, ABS and airbags, a four-system tool is often the better spend.

Does a listed reset function work on every car?

No. The menu is a catalogue, not a promise. Support still depends on the car, the ECU and the software version. Check the exact function before you order.

Should update terms affect the buying decision?

Yes. Find out what is included, what runs out, the UK renewal price, and what still works if you do not renew. “Free updates” and “lifetime use” are not the same sentence.

General guidance, not professional advice.