Honda 225hp Check Engine Light but no codes

Well, there are about 16 or 17 different sensors on this engine.


Normally, when the check engine light comes on, you should get a warning alarm. The MIL (or check engine) light signals that there is a problem with the programmed fuel injection system, which could be any of dozens of situations. Dr. H should identify the specific problem.

Do you have a four light console (oil pressure, alternator, overheat, MIL (check engine), or only two?

When you turn on the key switch, do you get two rapid beeps, then the alternator light comes on? And once the engine is started, the alternator light goes off and the green oil pressure light comes on?

The engine only goes into "limp" mode (i.e 1800 rpm) when there is low oil pressure or an overheat. If low oil pressure, it will continue to run at 1800 rpm. If overheat, it will shut down after 20 seconds.

On some of the early 225's, the check engine light will come on, but no alarm sounds when the HO2 sensor fails, but the Dr. H should see that if that's the case. That will also happen if your fuel pressure is out of spec. Fuel pressure at idle should be 42 - 49 psi. I'm not sure if Dr. H checks the fuel pressure, and I'm not sure it can. You might want to check the fuel pressure at the pressure relief bolt that is on the cover to the high pressure fuel filter.

BTW - you seldom ever need to change the on board fuel-water separator. Just clean it in fresh fuel.

Hi Chawk Man

Thanks so much for taking your time to help. Re the Fuel Water separator it was rusty at the top so we replaced it with is plastic so no rust.

So... We have a development with the Red Light!!!

I had another (fantastic) engineer take a look and we have got to the bottom of it.

"[FONT=arial, sans-serif]Put the boat in the water this afternoon so i could run the engine properly. With it plugged into Dr H i could see the thermostats opening and closing so the cooling system is fine, but could only get rid of the MIL light by disconnecting the harness. I had a look in the console and discovered a wire has been connected to the mil lamp wire, labeled "split charge relay" so it looks like it is telling you the house battery is being charged. Not the best way of doing it as whoever added the wire used scotch lock connectors which leave the copper wire exposed to the elements. It's very difficult to trace or see where the wire goes or how it has been set up so to do it properly could involve pulling the electrics out and starting again, probably 2 days labour"

Weve chatted today and instead of rewiring hes going to tidy up the connection and remove the wire from the MIL light.


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Hmmmm. Don't quite understand that. Do you have the four light or two light key switch?

If the four light key switch, then there will be a separate wire to the ACG (alternator) light. If a two-wire key switch, then it's possible that the MIL light is set up to go on with either a problem with the fuel injection system, or the alternator, but I'm not sure of that.

Just for grins, it might be a good idea to test the output of your alternator.

If you get your hands on the Helm Shop Manual, there are very detailed and complete wiring diagrams at the back of the manual.