Dodge Repair Questions? Ask a Mechanic for Answers ASAP
anytime the check engine light flashes there is a code stored a basic code reader MAY NOT be able to get it and the old key cycle method WILL NOT get it, how are you determining there are no codes?
yes flashing of and on usually means a misfire, so the pcm HAD to have set a fault your code reader may not be able to read it, there are also around 40 computers on the WK2 grand Cherokee( 2011 and up) so if the pcm did not set anything it is possible the other computers did the scanner you have is pretty basic you may need a more advanced tool to pull any codes set, a dealer level scanner can access all the computers, also did you happen to change the spark plugs to a "performance" set?
the hemi IS NOT tolerant to a different spark plug other than what was originally installed
first step is see what codes are setting anything else will be a waste of time and money, IF the plug seated correctly and clicked inplace (you heard and felt the click) the red tab is not really needed it is a SECONDARY lock and is used to be sure the plug seated correctly, I have seen tons of the red tabs missing and broken no big deal it is possible the performance chip damaged the pcm internally as we made significant changes internally to the computer between 08 and 11, it is faster and the pinouts have changed a bit from 08