2 X BOSCH PRE CATALYTIC OXYGEN O2 SENSOR FOR FORD LTD AU BA BF BARRA 220 230 WINDSOR OHV 5.0L 5.4 V8Pre cat O2 sensors are manufactured utilizing proven OE technology and are guaranteed to provide durable and efficient performance. The pre catalytic oxygen sensor is located before the catalytic converter and directly analyses the emission coming from the engine. It measures the oxygen content in the exhaust gases of an engine. Based on the output, it works together with the electronic control unit (ECU) and fuel injection system to control and