I have a 2004 Sonata (EF) 4cyl auto with 108K miles.
While driving, the car started missing badly and losing power. The check engine light came on steady.

I borrowed a code scanner and found four codes. P0300, P0303, P0302, and P0350
I went ahead and replaced the spark plugs, then spayed water on the area in a dark garage and did not see any arching.
I tested the coils and found that the coil feeding cyls 2 and 3 was bad. I replaced the coil, reset the codes and during the test drive the car ran very well for 10 miles before the problem returned. The check engine light came on steady.

Retesting for codes stored found one code. P0350.
I tested the coil connector and found proper voltage at pin 1 and ground at pin 2 for each. I did find resistance between pins 1 and three at each connector, but Hyundai says it should read infinite.
I did check all connections and look for any questionable wiring and found none.

My completely un-educated 'guess' is that their is a problem at the PCM.
Any ideas out there?

I have no idea where the PCM is, or how to get to it to continue testing.

Having no fun at all,

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