Ok, so in the PDF service manual for the 05 it says:
'When the C24/25/26/27 codes are produced, it's an ignition signal. The CKP sensor (pick-up coil) signal is produced, but signal from ignition coil is interrupted continuous by 8 times or more. In this case, the code C24/25/26/27 is indicated. To Check: Ignition coil, wiring/coupler connection, power supply from the battery.'
The battery itself is okay, but would the stator be next in line in terms of power supply?
Usually in those kind of scenarios, the ECU sees the CKP signal, but no signal from the coils for 8 times. The manual is a bit loose on this. It doesn't specify that the signal interruption is all 4, or will pinpoint which one. I would hope that it would pinpoint.
The ignition isn't all that complicated. Since you're just getting 2 codes, we can focus on the coils and ECU. All the coils share the same power source on the primary. Each primary is then ground coupled via the transistor in the ECU. Again, the actual ground is shared. All of the secondaries on the coils share this power source as well, and ground across the spark plug gap to the engine.
I think there's something missing, but I'd have to do a test on my bike to confirm. My assumption is if you remove the connection to one of the coils, would the ECU code for that coil? If it does, then there's another circuit in the ECU that does a detection.
Back to your problem. You get only 2 codes. If my above assumption is correct, you've got a fixed list of possibilities.
1) The ECU is bad. Either the triggering or detection circuits are a problem.
2) The coils are bad. Assuming the detection is looking for a specific resistance level from the coil, you're getting out of range somehow.
3) Related to #2, a poor connection in the harness connections. Bad connections raise resistance.
4) Bad connections internal to the harness. 1 wire is going to four. They accomplish this by crimp splicing in the harness. A resistance measurement from the coil power feeds to the engine stop switch should read near 0. If there is variation, those connections might be corroded/compromised within the harness.
As I'm studying this diagram and thinking about it, if it was the CKP or CMP, it should hit all four coils. Frankly, if it was anything outside the individual coil circuits themselves (KS switch, key cylinder, kill switch, etc.) it should code across all four. Because you're only getting two codes, there must be some sort of detection in the ECU. That limits the problem options to the ECU, the coils, or the wiring between them.