19. A system, comprising:
a more-upstream exhaust gas oxygen sensor;
a more-downstream exhaust gas oxygen sensor;
an emission control device; and
a controller with instructions executable to:
during a first condition comprising decreased scavenging, adjusting fuel injection based on a more-upstream air-fuel ratio;
during a second condition comprising increased scavenging, stopping monitoring of the emission control device, and adjusting
fuel injection based on one or more more-downstream air-fuel ratios and not based on the more-upstream air-fuel ratio.