Ошибка P0174: слишком бедная топливовоздушная смесь (банк 2)

With closed-loop control the engine module corrects the injected fuel using the oxygen sensor: short-term fuel trim reacts within fractions of a second, long-term trim stores a learned base correction per load and speed range. Positive values mean fuel is being added because the mixture was lean, negative values mean fuel is being removed; around ±10 % is normal. P0174 is the bank 2 counterpart of P0171 and only exists on V and boxer engines with separate mixture control per bank. The limits match: GM a long-term factor of about 1.30 (engine-specific), Ford above +25 % with short-term trim above +1 %; an older Saab V6 flagged more than 25 % deviation for 20 s. Two trips, no limp mode. P0174 alone points to a leak, injector or exhaust leak on bank 2; together with P0171 to a shared cause such as the air flow sensor, fuel pressure or crankcase ventilation – exactly what several GM bulletins describe. Diagnosis hint: trims very high only at idle and normal under load point to an air leak; trims rising with load point to fuel shortage or an air flow sensor reading low. The oxygen sensor only reports what is in the exhaust and is rarely the cause.