Code P2191 indicates that the engine control module has detected a lean air-fuel mixture on Bank 1 specifically during high-load conditions. This means there is either too much air entering the combustion chamber or insufficient fuel being delivered when the engine is under stress.
Air entering the intake manifold after the mass air flow sensor, often through cracked hoses or leaking intake gaskets.
A dirty mass air flow sensor may under-report the volume of air entering the engine during high-flow periods.
A clogged fuel filter or failing fuel pump that cannot maintain required pressure and volume under high load.
Partial blockage in Bank 1 injectors preventing the necessary fuel volume from reaching the cylinders.
Improper fuel maps or timing settings in the engine software that result in lean conditions during load.
Internal failure of the engine control module causing incorrect fuel calculation (rare).
Usually not. The oxygen sensor is the component reporting the lean condition; the actual cause is typically an air leak or a fuel delivery problem.
Certain vacuum leaks or fuel pump restrictions only become significant when the engine requires maximum air and fuel volume to maintain performance.
No. It is extremely rare for the PCM to cause this code. Mechanical issues such as vacuum leaks or fuel pump failure are far more likely and should be ruled out first.