F1 code 25

[rdmnt2002]

Since the ECU is damaged, it may not know what it is doing, it could fluctuate from lean to rich and all over the place.
The ones that I’ve had come through have all been dangerously lean.
As stated in a prior comment, there is such a small percentage of ECU failures, compared to how many bikes are on the road, it’s my belief that the ones that fail are usually on bikes that have a lot of add on electrical stuff, or bikes that have been ridden more than serviced, and are neglected.
I have not seen a single ECU failure on a bone stock, well maintained bike yet.
And I’ve seen more high mileage bikes in the 100-200k mile range still running perfectly.
It’s an electrical part like a light bulb. Nobody will now when it will burn out.
As far as the mpg going down, that could be a frozen t-stat from lack of service.

Thanks Larry!!

 

[Gus1300]

And I wonder how much heat damage I’d find on your bike…

I planned to retire in Jan and take a trip west for you to find out (hopefully you're back on your feet!) but just took another position that will delay that for 18 mos...but I still plan on making that happen, and we'll both report back here with the result! Looking forward to it...

And I concur to not ride the bike with the light illuminated; there is definitely a different feel/sound/power/response on mine when it is triggered, the throttle becomes 'jerky' unlike when the light is not illuminated. Normally it's very smooth when finely adjusting RPM to stay just a hair below 4k; not so after the light has come on and sometimes (but not always) for a while after resetting it (power cycle) until the ECU returns to some prior state and all is smooth again. I could see where riding in that illuminated condition wouldn't be healthy for the bike. I don't do that and wouldn't recommend anyone else do it either.

Possibly also guilty of riding more than maintaining; hoping to take care of some of that over the winter once the NoVA roads/temps prevent riding, but as of today, no sign of that on the horizon.

Not a lot of electrical stuff added on (not sure what constitutes 'a lot') but some: Audiovox cruise that no longer works, Stebel horn through a relay, security system and mirror cover turn signal LEDs the PO installed prior to me purchasing the bike. No LED power supplies or dash mount power leads. Some of that needs cleaning up as well but again, just a data point. I had no issues with the light for several years after purchasing the bike, and again no issues until a year or so after the first replaced unit. I just choose not to replace it again at this point. YMMV.

 

[Raia]

Welcome Hugo, and I am sorry to hear about your situation.

During your test ride, do you recall whether you rode at sustained RPMs above 4,000? If not, the FI light might not have come on. Usually, a knock sensor code of 25 or 26 is a sign that the PGM-FI unit has gone bad, but not always. I hate to disparage someone I do not know, but this seller may have knowingly failed to disclose this problem. When my ECM went bad, the unit would reset each time I turned off the ignition. If the code has been stored in the ECM (i.e., the FI light flashes without the engine running), then it could mean that something else is causing the problem.

In some cases, owners have found the wiring from the knock sensor to the ECM had shorted, and in others, the ECM threw codes because of low battery voltage. There are about a half-dozen diagnostics you can do to verify whether you have an ECM failure. However, if the FI light comes on when you maintain sustained RPM's above 4,000 for ten or more seconds, then it's likely you have a bad ECM. In my case, I had three options: keep riding it as is, replace the ECM, or part it out. However, replacement ECMs are difficult to find because Honda has discontinued their production for model years 2003-2007.

Whether the bike is safe to ride with a bad ECM has been the subject of much discussion on this forum. Two of the most knowledgeable members, @Igofar and @aniwack , do not agree on this matter. Some owners have been riding their STs with bad ECMs for years and claim not to notice any problems other than a significant drop in fuel mileage. Other owners have reported that the bike runs hotter than usual, which has resulted in melted wiring and fairings. As for myself, I found a seller in Japan that had a NOS ECM for the US Police STs that will work on my '05 ST13 and had it imported to the States. Because some of the European models have HISS, I cannot say whether this is an option for your Pan.

I sincerely hope your problem is not a faulty ECM. My failure happened at around 92,000 miles (140,000 Km), but I have seen reports where failures have occurred with fewer miles (Kms) like your bike. Why does this problem happen? No one is quite certain. Nevertheless, the ST is not the only Honda model to experience ECM failures. Hopefully, you can find a solution.

Chris

I have an 2003 and at 92,000 the f1 code started also.

 

[RobbieAG]

there is definitely a different feel/sound/power/response on mine when it is triggered, the throttle becomes 'jerky' unlike when the light is not illuminated.

I don't notice this at all. Mine runs normally for the most part. One thing I noticed is that the mpgs are now pinned at 40 mpg whether the light is on or not. It used to be 42 - 43.