So, 04 Grand Cherokee, has been running pretty bad for about a week now. I have ruled out bad gas (it's been through a tank and a half now), i replaced the spark plugs five days ago, and just replaced the fuel injector today for cylinder #2. each time i do something to it it runs beautifully for about ten miles, then the check engine light comes on and the engine starts spuddering like its missing on one or more cylinders. i have had the trouble code read by a hand held code reader three separate times and each time it throws the same thing P0202: injector two circuit open/malfunction. I am my witts end on this. if the coil pack was messed up, both cylinders on that coil would be misfiring, right? i'm starting to think its a problem in the ECM? i hope not. $339 bucks im not really wanting to spend right now. Any advice?