Buick LaCrosse Oxygen Sensor Rear 12621696 Direct replacement OEM standard

Buick Lacrosse rear oxygen sensor (OEM 12621696) located downstream of the catalytic converter in the exhaust pipe; monitors oxygen content after catalytic conversion to verify converter efficiency and feed back to the ECU for fine-tuning fuel injection. Direct replacement of the original standard part, no wiring or bracket modifications needed; compatible with multiple model years of Lacrosse. Installation steps include disconnecting the battery negative, removing the old sensor, applying anti-seize compound, and tightening the new unit. When fuel consumption rises abnormally, there is a pungent odor in the exhaust, or the engine warning light stays on, it is recommended to check this sensor first.