10/10 on the test.
I'm sure I don't need to say this but remember pin 16 on the OBD port is always live so leaving your bluetooth plugged in when not driving = flat battery eventually.

 

Got it! Pending codes 0304, 1316 and 0354. Looks like the #4 coil. Odd, that's the one I replaced 2 years ago...

 

Nice, glad you caught it. Was your coil a poor quality brand?

 

Must have been! It was a Beck/Arnley product. I recognize the name from years ago but, honestly, who knows where anything comes from these days. It had a 1 year warranty.

Two years ago the other selections from Rock Auto were from companies I had either never heard of (and were more exensive) or were from companies that I didn't associate with quality stuff.

The same is true today and, perhaps foolishly, I ordered another $65 Beck/Arnley product. There's a significant price bump to the next leveL - ~$85.

It's not a hard part to find, Autozone had them for $113 from two different manufacturers that I've never heard of...

 

Did the codes appear + disappear while driving?
Let us know if you get a cure.

 

Here's the sequence of events...

First I would get an periodc RP message along with a short sequence of a flashing CEL light. This event would last just a few seconds and happen once or twice a week. No codes.

Then it escalated to happening almost very drive cycle and the flashing CEL would stay on for longer periods of time. I changed the spark plugs, cleaned the MAFS and the throttle body. For that, I was rewarded wth RP, the flashing CEL light and Pending codes P0304, P1316 and P0354.

I swapped the 4th cylinder coil position with position #3 and was able to trip the CEL light with active code P0353.

I'm pretty sure it is a failing coil. On it's way out it can cause a flashing CEL and RP which indicates a developing misfire situation but does not set codes. Eventually, Pendng codes will be set and later the actve code with CEL light will occur.

Pretty logical, I guess.