JK Wrangler Misfires Rough Idle DTC Codes p0303 P0203 code-- SOLVED
 

Ok so I think I have found the solution to many of the misfire, intermittent rough running, running like crap, red lighting bolt electrical gremlins. Let me first say I have red 50+ threads on the weird issues people are having throwing codes one day and then running ok another day. They like me have replaced every sensor, plugs, wires, coil and then take it to the stealership where they haven't got a clue either they just make you replace the PCM and anything else they can think of.
I started off having the red lighting bolt which I red could be a multitude of things but most pointed to the coolant temp sensor because my fan also wasn't coming on when it should. I replaced that and it went away for a day or two and then came back on. Still fan not coming on. Then it started running really bad......like a blown head gasket bad. I just rebuilt this motor 4 months ago so I was really doubtful it was a head gasket. No water in the oil and no coolant smell out the exhaust pipe. Pulled the plugs and did a compression test and checked the plugs for possible coolant burning. All cylinders around 160 psi. Plugs look like new. Checked coil and I wasn't getting anything out of number 2 for spark. Replaced the coil, ran better but still horrible miss. I had got different codes every time I reset the PCM and restarted. Most all included P0202 and P0303 both issues related to injector number 3 misfire. Finally I just said fine I will pull the intake and see if I see any wiring issues or anything out of the ordinary. Pulled the fuel rail and disconnected all the injectors. Well most of the connectors had water in them from may pressure washing the engine or the when I installed the angry grille and never installed the rubber flap that goes between the grille and the hood. So I decided to blow out the connectors and the injectors and then noticed injector 3 had a broke pin in the injector and was lodged into the connector was not making contact. """Boom I think I found the problem for sure"""" Right? Not so fast.
Since I had moisture in those connectors I decided to check the large connector that goes from the fuel injection harness to the main loom. Below you can see what I found. The three large wires on the outer area of the connector had completely corroded away and the inside of the male and female connector had green corrosion. Looked like this had been a long time in the works. That right there could set off all kinds of issues with the PCM and drive ability. I'm waiting on an injector and pigtail that should be here friday so we will see. As far as these three wires. My options were basically get a new injection harness and new main harness or cut those three wires and wire them together outside the main connector which is what I'm doing. I will update this week and share the youtube vid when its all done but I hope this helps some people out because I know I can't be the only one with this problem.

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Replaced the injector and pigtail today in addition to rewiring the the 3 wires which ended up being the br/wh was the ground for all the injectors. The br/blu which went to a few of the injectors as did the br/yl. All important wires and now the Jeep runs like brand new. Better than ever. So happy.

Good find! Electrical gremlins are the worst.

I admire your tenacity and ingenuity on this. Intermittent problems like this are a pain to troubleshoot. Good job on keeping with it, and thanks for letting us know what it was.

Good work! :beer: