Selfclearing fault codes

[spongebob]

How does it work with some fault codes?
Can they be completely self erasing if the status becomes ok again after a fault ?
I read two codes a while ago P0430 ( cat conv. Bank 2) and P0159 ( sensor aging) when the Check engine light turned on.
Never cleared them however. But after topping up with fuel, the Check engine light went back to normal ( no light ) . All looked good-for some hours but the suddenly the CEL came back on. Same codes when checking.
Are some codes self-clearing and others not ?

[JFP in PA]

Yes............

[spongebob]

Originally Posted by JFP in PA

Yes............

Thanks,
Just assuming it is the P0430 that is coming and going.
Meaning that the engine is running lean now and then.
Could it be the fuel pump being worn and only delivering enough pressure when tank is full?

[JFP in PA]

Only way to know is to run fuel pressure and volume delivery tests.