can anyone help with the problem on my sportster 1200 type s, suddenly the rear spark plug goes out, I have updated the module and cam position sensor but it's still dead

 

what year?
stock ignition or after market?
the stock does produce codes via the speedo. the coil is a single fire dual tower per cylinder. make sure your connections are clean.
redneck test. remove the terminal going from the effected cylinder to the module, remove plug and ground shell, take a jumper and flash 12 volts to the bare terminal, the plug should fire.
if not, remove the wire from the other plug and repeat.
here is the kicker, if one plug shorts, it takes out the other, been there done that with some NGK plugs.
my sport is hot and i got into it with two cagers, they couldn't keep up, cannot tell how fast since the clock runs out at 120 at 5k and when i drop into 4th, the clock is history. anywho, they gave up and i turned around to go home, stopped at a light to turn and the machine started one lunging but i got it home. i had one ultima failure so i thought it was a second but not the issue as everything checked out. pulled the plugs and one was high resistance to the electrode and shell. when a plug is hot, requires less to fire, changed and now ready to find the next yahoo.