P0003, P0300, P0302, P0303, & C0300

First got P0303 & P0300(P). Reset check-engine light and a few minutes later got P0003, P0300, P0302, P0303, & C0300. No coolant leak, oil is at the lower dipstick mark but ok and clean, last tank was 48+ MPG. Noticed slight audible valve rattle for the past couple of months but no CEL until this week. Rattle lessens when engine is warm.

Heard this could be a Low Aux battery, though that was replaced 1+ year ago, and there are no other symptoms of low voltage. Coolant is not leaking (this car had HG job done 35k miles ago, so I know the signs). Also read that EGR circuit could need cleaning, MAF sensor, throttle body, etc? At first I thought P0303 signified a simple spark plug job, but it got new plugs 15k ago, and the additional codes seem to suggest another solution, especially P0003 and C0300 which I have never seen before.

Thank you to anyone who has had these codes and can advise.

 

Thanks. Do you know what the P0003 & C0300 codes might mean in addition to the associated cylinder(s) misfiring?

 

Thanks. I have changed the plugs before but last time one broke off at the ceramic; mechanic was able to get it out; so no more of that for me, I'll take it in thanks.

 

I have inspected the wiring and there are no mice-chewed wires or hoses that I can see from a top-view visual inspection. I've heard that cleaning the MAF sensor might rectify this issue, but I haven't had luck with this solution when my other cars have had similar problems, though I may try it if recommended. I cleared the codes again and I'll drive it until they come back on (not driving much at all these days due to current virus situation). Likely to take it to the shop in a day or two.

 

Correct.

 

No not to my knowledge. Correct. Correct.

 

Erased the codes and drove pretty hard both highway and city for about 40 minutes today. Haven't come back yet. Put a bottle of Techron. I'm convinced it's either dirty EGR, or bad battery. We'll see.

 

UPDATE: Since erasing the codes have driven about 120 miles, hwy and city, codes have not come back. Bottle of Techron currently in the tank. Seems to run a little smoother. Current working theory is either Low Aux Battery, or clogged Fuel Injectors. If codes come back I'll try cleaning MAF, though I've never had much luck doing that on other cars.