2007 FLHTCU. Stock internals w/ PCIII tuner, high flow intake and Rinehart true duals.
I recently replaced the IAC as the bike would stutter when coming to a stop. Cleaning it several times helped, but never solved the issue.
Replacing it did.
Never touched the idle stop screw as others recommended, although I did buy the 5-pointed bit & show it to the bike as a threat.
Also experienced poor starting on multiple occassions, just replaced the battery and that seems to have helped resolve that issue.

Now the only issue that remains is a CEL that throws NO code.
Without a code, how do I even begin to figure out why the CEL is on?
What good would using a reader/scanner be if there is no code?

 

I wonder if there is an off chance that the ECU hasn't synchronized with the IAC or vice versa. Perhaps try cycling the ignition arming toggle with your dash panel switch remaining on. With my Thundermax it was kinda like 30 seconds on, 30 seconds off for about 5 cycles. That is what instructions specified to sync the two. Worth a try I think. You might have to disconnect your battery ahead of doing this then reconnect. Another method may be to find your main fuse, pull it, leave it pulled for a minute or two and then perform the sync with it and the battery reconnected. Nothing ventured. Nothing gained.

 

Thanks to another member, i was alerted to the method that I was checking for codes. The run switch must ne ON/RUN in order for at least some codes to appear.
I reran the test and found code P0117.
The next step was to measure for 5VDC at the plug to the temp sensor.
I had 5V, so the next thing I did was to replace the sensor w/ the original one.

Bike fired up and the CEL is GONE!

I replaced the temp sensor earlier this year to help w/ a cold start issue.
Turns out that my battery was beginning to fail and now the replacement temp sensor has failed.

New battery and old sensor seemed to be the right combination to resolve this issue.