Driving to lunch and the CEL came on. Car/engine has been running just great. I switched to Chevon gas because my favored Shell station raised its prices by 20 cents/gallon for some reason. The Chevron gasoline after some few tankfuls really perked up the engine. Techron is no joke.
Read the error code just now and as I said above: P1128. I cleared it and sat there thinking. I remembered adding some oil the other day and on a hunch I checked the oil filler tube cap. It was secure. But then I remembered a few years back and tried the cap to see if I could cause an air leak. Sure enough if I pulled up on the cap I could hear air rushing past the cap. I pushed down and the noise stopped. I pulled up again and let go and the cap stayed up and the noise remained. I pushed it down and the noise went away again.
This will be my second oil filler tube cap. The original one wore out and now its replacement.