I have a Grand Cherokee, 4.0L, 89,500 miles. About six months ago, I was on the highway when it misfired, check engine started flashing. I immediately got it to the dealer who diagnosed cylinder misfire #6 and "fuel injector cuts out electrically". PCM was replaced.
All was well until recently, when I started to notice an occasional rough idle. Then it happened, again, cylinder misfire and flashing check engine. The dealer said the code was P0305B, cylinder #5 misfire, and said it may have attributed to bad gas. Filled the tank, added dry gas, injector cleaner, and was fine for a couple of days when the same thing happened. I then brought it to a different shop. He pulled up the P0305B code and P0205 injector circuit cylinder #5. The injector resistance, wiring and pulse were checked with no problems. Throttle position sensor was checked and found to be OK. He suggested it was a possible bad PCM and to go back to the dealer, which I did. The PCM was under warranty, so he replaced it. Picked it up, drove it, and again, cylinder misfire and flashing check engine.
It starts fine, the problem seems to occur when the engine is at operating temperature after a warm start. I'm reluctant to go back to the dealer.