I have a 2007 Pontiac G5 GT 2.4 L Ecotec 132,200 miles. Had since new been a pretty reliable trouble free car up till now. Out of the blue with no warning instantly started missing very bad check engine light instantly came on then started flashing. Luckily only about a mile from home. Some exhaust smoke think unburned fuel or rich from misfires. I have a blue driver scanned 2 codes PO300 random multiple misfires and PO202 cylinder 2 injector circuit. First thing I did was check battery with 2 different battery testers both showed good battery so ruled that out. Anyone have any ideas. Luckily it’s a second car so have time to tinker with it. Also no water in oil and no oil or bubbles or lost antifreeze. So don’t think head gasket.
PO202 fuel injector circuit cylinder 2 is causing your misfires. There's a problem with the fuel injector circuit electronics. Check the wiring to that injector for corrosion, broken wires and such.
Another thing you might try is moving the injector from cylinder 2 to cylinder 1, if it's possible, and see if the code moves, the same way you would diagnose a bad coil. If you can actually do it, and the code becomes P0201, that injector is bad.
PO202 cylinder 2 injector circuit.
that should be your first clue. (it's P-number zero , by the way, not P-letter oh)
And since you have multiple cylinder misfire, you might as well check them all.
https://www.youtube.com/watch?v=XhYEDkpF3Qs
