C25-coil fault but the coil isn't the problem? Pointy

Originally Posted by Red ones

I think the lights are supposed to go out on start up. Always have on my K5

Glad to hear that one, ever since my first days on an '89 TZR125 nearly 20 odd years ago, I've sworn by riding with the lights on but never agreed with recent bikes not having the option to turn them off, especially on starting.

Thanks for that

[Bibio]

the ECU will throw a code for any part of the chain it finds a fault with in your case it's giving a C25, this may or may not be the coil and can be any part of the chain from the ECU to the plug on that circuit.

swap the good plug from the front into the rear and visa-versa then see what happens.

don't change coils or do anything else till you know for definite that it's not the plugs. once the plugs are ruled out than trace the line back till you find the fault.

[Red ones]

Originally Posted by Bibio

swap the good plug from the front into the rear and visa-versa then see what happens.

And be prepared to take the skin off your knuckles! Serious tip- take the rear plug out first, it saves an extra trip to the front plug and having to inflict more pain on your hands. You may gather I'm not a fan of changing the front plug!

TBH you would need some seriously duff plugs at that mileage. Despite what the manual says you should be able to get 30,000 miles out of a set of plugs. But it is worth checking. I'd also check for loose connections on that circuit. It really shouldn't be major at that mileage unless.... Do you keep the bike in a garage? Does the garage have any sign of mouse activity?

[Sid Squid]

There will not be a fault code if the plug is duffed obviously, but clearly it would be worthwhile to rule them out - particularly if one of them is very old or perhaps the age of the bike.
From what you've written the problem lies in the coil circuit, be that ECU, wiring, connectors, coil.
When the bike is in a run state you should get voltage on the hot side of the LT, (as you likely know the coil negative is switched to give sparks), check the voltage there but make sure the system is lived, in many permutations of the start/run inhibitors the system is effectively switched off, so make sure there's voltage at the hot LT on other coil when testing.
As you suggest, it would make sense to swap the coils over so the known good coil is in the suspect part of the system - that would be my first move, then check the wiring from the coil back to the ECU.

An aside:

The SV has a number of 'limp modes', for instance if the barometric sensor, either temperature sensor, gear position sensor, throttle position sensor or the secondary throttle servo fails the system will default to a preset value and run with that. On the SV1000 there are some failures the system can deal with while the engine is running, but it will not restart if switched off.

[yorkie_chris]

I've seen more coil faults that are faulty coils WITHOUT giving a coil fault code including completely open-circuit coils.

Don't think the ECU coil-fault-sensing-jobby is very clever.


Broken wire/shorted connector/rusty connector/ECU fault...

Thanks for all the info guys....

So far yesterday....
Changed the spark plug, still on one....
Changed the coil, still on one....
Checked power to the coil, 12 volts.....
Checked the ECM to coil wire, no break....

Nothing else is in the circuit according to Haynes so the only thing I'm left with is a faulty ECM....

Only problem with that is, with the positive and negative removed from the rear coil, I get one cylinder running (obviously) but no FI warning.
With the wiring all hooked up and the bike fired into life, starts on one cylinder and the FI warning is immediately up (C25).

I'm either looking at the ECM not being faulty as I personally would expect the FI warning C25 without the coil connected (blanket C25 faulting on that mircocircuit regardless of what is or isn't connected, not having a coil connected is a pretty big fault in my eyes!)...
Or there is a fault with the ECM, it just doesn't have the complete circuit to give the FI warning without the coil connected (ie, needing all the components connected to validate giving the warning in the first place)...

Anyone have an idea of which is more likely?

Easy answer would be to plug my suspect ECM into a donor bike and see if it runs on one but don't know of anyone with a local SV650 or trusting enough to do that with (maybe I'll go to a local bike shop with an SV650 for sale and take it for a test ride then try my ECM on it around the corner)

Better still take it back with a faulty ECM------

Originally Posted by Dicky Ticker

Better still take it back with a faulty ECM------

lol, nice

Suppose one question I could ask the community to help with....

Anyone out there with a working bike willing to disconnect the positive and negative on the end of the rear coil on their K2/3/4/5/6 (right side frame between the coil and regulator) and tell me if it runs on one cylinder with no FI fault or one cylinder with FI coming up?

At least I'll then know if the disconnected coil should create the FI warning or not (as it currently isn't).

[yorkie_chris]

I had one the other week which was running on one pot, infinite resistance on coil primary. No fault code. Cured with new coil.

Originally Posted by yorkie_chris

I had one the other week which was running on one pot, infinite resistance on coil primary. No fault code. Cured with new coil.

Yeah, I'd be happy with that sort of result but still getting a fault code (and thus the ECM blocking the ignition of the coil, even if it isn't physically faulty) after having changed the coil and plug plus testing through the wiring really sucks!

Beginning to think it could only be the ECM at fault.