DoIP: why an OBD-II scanner is nearly useless on new cars
In new cars diagnostics moved from the slow bus to Ethernet, and a cheap adapter there reads only the emissions minimum required by law. What that means in practice and what not to expect from a scanner.
Someone buys an adapter for a 2023 car, plugs it in — and sees four readings and an empty fault list. The adapter is fine, the software is fine. The diagnostics of that car simply no longer live there.
What DoIP is
DoIP is diagnostics over Ethernet — the same Ethernet as in a computer network. UDS runs on top of it: the language control units speak to a dealer tool. It is orders of magnitude faster than the ordinary CAN bus, so everything heavy moved there: unit firmware, calibrations, whole log downloads.
What matters for us is different: it is another transport. A cheap OBD-II adapter can talk CAN and cannot talk Ethernet at all — not because it is «bad», but because it has neither the pins nor the chip for it.
What is still available
The emissions minimum has not gone anywhere: by law the car must answer standard OBD-II requests — emissions-related codes, readiness monitors, some live data. So engine speed, coolant temperature and readiness show up even on the newest car.
What will not be there:
- ABS, airbag and body electronics faults;
- service procedures: service interval reset, brake bleeding, adaptations;
- factory logs and calibrations.
That is not a limitation of the software. It is the boundary of the transport, and no app gets around it — we say so plainly, because promising otherwise would be dishonest.
Telling «no access» from «the car is asleep»
| What you see | What it is | What to do |
|---|---|---|
| Every bus silent, adapter answers | Ignition off, or CAN-FD | Switch the ignition on; about CAN-FD |
| 1–2 units answer out of ten | The rest are on other buses | Normal for new and Chinese cars |
| No emissions faults, but the lamp is on | A fault in a unit unreachable from the socket | A dealer tool is needed |
Research and «workshop» modes
New platforms have dealer access modes, and they are studied openly. For the Geely EX5, for one, there is a public firmware teardown: processor architecture, UDS over DoIP, SecurityAccess, and a mention of a separate «workshop» transport path.
⛔ We do not publish the activation codes for such modes that circulate on forums, and we do not advise repeating them — for two reasons. First: we have not tested them, and an untested recipe in an article means the reader carries the consequences. Second: a car can be left in a dealer mode, and getting it out may cost a dealer visit. The author of that research, incidentally, states explicitly that the work was done on his own car and is not an instruction.
What we do on our side
DoIP packet parsing in the app is already written — both platforms, checks down to individual bytes. But ⚠️ it has not been verified on a live car: we have no DoIP platform at hand. So we do not claim to «support DoIP» — that would be a promise on trust.
If you have a car on a newer platform and feel like helping, a session log from the app would be very useful. It is taken from the app itself and contains nothing but the exchange with the car.
If you are choosing an adapter now
Look not at «version 2.1 versus 1.5» but at what is said about buses: which adapter to choose and where the socket wires go. For a recent car the question is different from ten years ago: not «will it read» but «which units will it reach».
