‘97 FLHTCUI , original MM efi system (Gen 1). Starts, runs, no issues with original Dual-fire coil. Installed a Single-fire coil ONLY. Key on, fuel pump spins up, START. Engine light goes out (because it is now running) and within about 3 seconds, Engine light comes on, doesn’t clear. Re-connected Dual-fire coil, NO Engine light. Re-connect Single-fire, Engine light comes on within a few seconds. Engine runs great with Single-fire coil. Snappy throttle, crisp, smooth. Tach works and responds to throttle. Oil pressure above 20, Volts above 13, efi cold idle settles down to warm idle as expected. Have NOT taken it out for a ride.

NO, you can not talk me into doing the “carb swap” YET. This MM system is running great. Push comes to shove, I’ll leave the Dual-fire installed.

So, What is the difference with Dual to Single in respect to what the ECM is or is not sensing? Is it a “learning curve” for the ECM?

I appreciate all constructive comments.

 

I learned something here, measure the resistance on both coils, always thought M&M was single fire only, dual and single fire coils have different resistance and most likely the ECM is detecting the lack or higher resistance when firing, the M&M can detect a coil miss fire in cylinder 1 or 2 so the signal wires from the ECM are separate. Answer, it is just picking up resistance out of designed specs.

 

Makes sense, don't know what you can do to remedy it.

 

I think you may be correct. MM is single fire coil. A more in depth search, after seeing your comment, shows that the efi system is a single fire system. My bad there. I measured the resistance across the factory coil @ 5.57ohms each side. My research for a ignition system upgrade stopped short, apparently. Now, I have a 3ohm single fire coil in my parts stock.

 

Maybe 10mm wires would help.