Q: I got code P0016 and P0008. I just want to know what caused the problem and which one is bank 1 sensor A?

Hello, this problem (both codes apply to the same problem) relates to a calculated "bad timing correlation" between the crankshaft and the exhaust camshaft for cylinder 1 (cylinder head at front of the car). Engine management has tolerances for the position of each cam in relation to the crankshaft at top dead center, and it is checked every revolution of the engine.

Timing chain stretch (which is certainly an issue with your mileage), cam phaser adjustments to cam timing, and timing chain tensioner wear all effect this relationship. With your advanced mileage, I suspect the timing chain guides, and timing chain stretch, have allowed the mis-alignment to creep up until it exceeded the threshold. The timing chain components need to be rebuilt/replaced.

There is a GM Technical Service Bulletin (330977) which MAY offer some financial relief for this repair, but I doubt it would be much with 195K miles on the odometer. I would recommend having a Check Engine Light inspection completed by a mobile, professional mechanic, such as one from YourMechanic, to confirm this diagnose, get an accurate assessment of damage and cost estimate for repairs.