Geely over OBD-II: what answers and what stays silent
A full sweep on a real car: two of twelve control units answer on the standard socket. Why that is not a fault, what you can still learn, and where «94 errors» on a healthy engine come from.
The short version: on a Geely Coolray, two of twelve control units answer through the standard OBD-II socket — the engine and the gearbox. The rest stay silent not because they are broken, but because they are not on that socket. Below is what we measured on a real car and what follows from it.
This is about the BMA platform: Coolray and relatives, 2019–2024. On newer models (EX5 and others on GEEA 3.0) diagnostics work differently, and none of this applies to them.
What we measured
A sweep on 6 September 2026, engine running, an ELM327 v2.3 over Bluetooth:
- bus: ISO 15765-4, CAN 11 bit, 500 kbit/s — the standard variant, detected automatically;
- voltage at the socket: 12.8–12.9 V;
- 2 of 12 units answered:
7E8engine (ECM),7E9gearbox (TCM); - we read both unit identifications, readiness monitors and 22 on-board test results;
- active faults: zero.
Why the rest stay silent
Silence on the diagnostic socket means one of two things: the unit is not on that bus at all, or the adapter cannot address it. Cheap ELM327 clones only manage the broadcast request 7DF and refuse to change the header.
Ours was the first case, and that is proven: the adapter accepted 311 header commands (ATSH) and 295 receive-filter commands (ATCRA), answering OK to every one. So addressing works. The instrument cluster stayed silent on both of its addresses — over a hundred addressed requests in a row, not a single reply.
Hence the honest conclusion: another ELM327 will not change this. A dealer tool sees the cluster not because it is «smarter», but because it has all socket pins wired and switches between buses. A cheap adapter has only pins 6 and 14 soldered — the CAN lines — and physically cannot reach the other buses.
Where «94 errors» on a healthy car come from
Ask the unit «how many faults do you have» with mask FF, and the engine answers 94, the gearbox 70. Meanwhile the list of faults for the same mask comes back empty, the lamp is off and the car drives fine.
The answer: mask FF counts not faults but every code with any status bit set — including «test not completed since the last clear», which is set for almost every code in the unit's catalogue until the car has driven its check cycle. After a battery disconnect or a code reset there are dozens of those immediately.
So «I have 94 errors» and «I have 94 faults» are completely different statements. What matters is active faults and the readiness monitors — the very thing an emissions test looks at.
What two units still give you
- engine and gearbox codes — most of what turns the check engine light on;
- live data: engine speed, coolant temperature, system voltage, fuel trims, load, air flow;
- readiness monitors before an emissions test;
- unit identification: firmware and calibration numbers.
What you will not get: ABS and airbag faults, service interval reset, adaptations and calibrations. That is dealer-tool work, and promising otherwise would be a lie.
If you are choosing what to buy
For codes and live data a plain ELM327 is enough — which adapter to choose and what to do if it will not connect. If you need units beyond the socket, you need a different class of tool, and no app replaces that.
To see what your car answers, check the profile for your model: the app runs exactly this sweep and lists the units that answered — together with those that did not.
