Chrysler Repair: Service engine light flashing:98 sebring 2.5 v6, metal surfaces, ground path

Question
evening roland.. i have always had a problem with this car when it rains heavy.  service engine light would come on flashing when i would go up even a slight hill in heavy rain.  had the computer checked and was told there were no codes stored for some reason.  disconnected the battery and connected it back up about half hr later and light would go out until the next time it rained heavy.  the other day i went someplace and shut off the car it was running good.  about 15 mins later got back in the car, started it and was missing, pinging, bucking and light came on flashing, and it wasn't raining.  got home and disconnected/reconnected the battery and still the same problem.  got gas the day before from the usual place, so don't think thats the problem.  any hints?  thanks

Answer
Hi Bob,
And good evening to you to, Sir, I hope you had a good Easter.
The absence of codes, assuming that is still the case, and the flashing of the light, and the humidity/rain coincidence, would lead me first to consider the battery cable post/clamp interfaces and tightness, and then I would check the main ground points for the powertrain and battery.
There are two ground wires attached to the top of the left strut tower and one on the right strut tower, and one at the seam between the engine and the transmission at about 2 o'clock as you look at the powertrain from the drivers side of the car. I would loosen, remove and clean all the eyelets and metal surfaces against which they are bolted to make sure you have good grounds. If that doesn't solve it then you would probably need to keep checking for fault codes, which should appear if you get a steady check engine light for any length of time. But that flashing really seems like a main problem with the battery supply source or the ground path back to the - post of the battery. If there is an Autozone parts store nearby you may be able to get a readout there. If the battery connections/grounds are flakey, by the way, that may cause a self-erase of any true codes so that may be why you can't get any codes.
Roland