The check engine light came on during a ride on your EX Sport, and when you connect and read the memory, there is nothing in it. This applies to the whole EX series from 2017, the EX, EX Sport, EX Deluxe and EX Limited, with the three-cylinder TR-1 engine. Owners across several models report the same thing, so you are not looking at something unusual.
Is the fault still there, or only remembered?
A fault the control unit saw once and no longer sees is different from one that is present now. The light and the memory don't always agree about it. In reports from owners, the typical explanation is a sporadic fault, one that appears for a moment and goes, or a stored fault that has already passed.
The light can also go out by itself. After several start and stop cycles with no repeat, the indicator may reset without anyone touching it. So a lit lamp with an empty list isn't necessarily a contradiction.
What I would try, in this order
Read the memory again after a short ride
A fault that only shows under load or vibration may not register while the boat sits still. Take a short ride, shut down and read again. If an entry appears, you have a direction. If it stays empty, move on.
Clean the connectors
Cleaning and reseating connectors often helps, according to a number of owners. A plug with a film of corrosion can drop out for a split second, and that is just enough to light the lamp without leaving a stored code. Start with the connectors you can reach easily: the throttle body, the coils, the injectors, the battery terminals.
Look at the live data
With the engine running, check battery voltage, temperatures, intake pressure and the switch states. A switch that flips back and forth, a voltage that dips under load, or two sensors that disagree gives away a flaky connection even if no code was stored.
Log a test ride
This is the one that catches intermittent trouble. Record a ride while it behaves the way it did when the lamp came on. Afterwards, find the moment the lamp lit up and look at what changed in that second.
What the app does here
The M-JET Diagnostic reads the fault memory of all EX variants and shows the live values and switch status that go with it. If you do find a code, it is described in plain language with the possible cause and test steps. Don't clear the memory before you have written down what was in it, since an entry that disappears is also a clue. The page on clearing the fault memory says when that is sensible, and the page on the EX with a lamp but no code goes into this case further.
Limits
Not every problem sets a code, and the light does not always have an electrical origin. A corroded plug with no code or an overfilled oil level won't necessarily show up in the data, and neither will the delivery rate of the fuel pump. If the light returns and every log is clean, the next step is physical: inspect the plugs and spark plugs, and check the oil level six minutes after a warm run on level ground.
