I had a flashing CEL and when read found P0301, P0302, P0303, P0304, and P1399.
The mechanic I took it to found that the coil pack in cylinder one was bad and the plug had the ground electrode burned away and showed tracking down the outside of the plug. I had replaced the original plugs with Bosch four (4) prong plugs; the mechanic replaced them with original plugs and said he'd not had good success with them. Not sure which caused the failure.

 

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