Got my car (2011 Mustang) and did this. After a 'set back', it is now working!
I had inadvertanly held the remote fob button too long an reset the all of bank 2 to defaults. I was then getting a "tach not learned" error when I tried to remote start the car. I put bank 2 option 1 back to On (i.e. tachless) and got it working.
Once I 'fixed' it, here are the steps I did did:
The remote override button is 'easy' to find. It is taped to a harness, kind of right under the steering column. The remote module is tie wrapped above the kick panel (black box). The LED is tapped to the same harness and is about 1 inch from that button (between the button and the remote start module). I found it was easier to lay my back onto my drivers seat and then slide under the dash. Once you find the override button it is easy to press while sitting in the seat. But the LED is hard to see when sitting. So this is my recommended approach:
1. sit in the car with the door closed (has to be closed to enter programming mode)
2. press and hold brake pedal (keep it pressed)
3. turn ignition key to run (one position from start which lights up all the guages)
4. reach under the dash and press and hold the override button until horn beeps 3 times (about 10 seconds)
5. after the three beeps, release the override button
6. release brake pedal
7. open the door and now lay on your back to get your head under the dash (so you can see the LED light up; it won't be lit yet, but once it is, it will be obvious).
8. press and release override button (horn beeps 4 times, indicating bank 1)
9. press and release override button (horn beeps 5 times, indicating bank 2)
10. press brake (horn beeps 1 time, indicating option 1). This is "Tach Mode". I believe the LED should be lit. This is the one I had to play with. The true default is off, but I had to turn it On after I reset to defaults.
11. press brake (horn beeps 2 times, option 2). LED should be lit.
12. press brake (horn beeps 3 times, option 3). LED should be off.
13. press brake (horn beeps 4 times, option 4). LED should be lit.
14. press brake (horn beeps 5 times, option 5). LED should be off.
15. press brake (horn beeps 6 times, option 6). LED should be lit.
16. press brake (horn beeps 7 times, option 7). LED should be lit. (this is the one you need to change.
17. press and release the button on the remote start fob. the LED will go off.
18. press brake (horn beeps 8 times, option 8). LED should be off.
19. climb out and turn ignition key to off and take the key out.
20. close door and remote start your car. things should be great now.