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Bank 2 is the drivers side of the engine Sensor 1 is in the exhaust before it enters the catalytic converter ( upstream )
It just has ( 1 ) oxygen sensor , before the catalytic converter ( upstream )
I'm not a mechanic / technician but on a 1988 Ford Ranger there might be ( 1 ) oxygen sensor ( upstream sensor )
Lack of upstream heated oxygen sensor switch - sensor indicates rich - bank no. 2
Upstream Oxygen Sensor Circuit Slow Response (Bank 1)
P1132Lack Of Upstream Heated Oxygen Sensor (HO 2 S 11) Switch, Sensor Indicates Rich (Bank#1)P1152Lack Of Upstream Heated Oxygen Sensor (HO 2 S 21) Switch, Sensor Indicates Rich (Bank #2)
my 99 e250 with 5.4 gas engine has 2 upstream sensors and 1 down stream sensor.
there are 2, upstream which is under the exaust manifold flanges and the downstream which is in the exaust pipe
It is the upstream(before catalytic converter) oxygen sensor on the exaust that comes off the front engine bank.
Bank 1 is the passenger side of the engine in your Ford Expedition Sensor 1 is in the exhaust system before the exhaust enters the catalytic converter ( upstream )
The oxygen sensors located before ( upstream ) of the catalytic converters are used to " sense " the amount of oxygen in the exhaust to adjust the air / fuel ratio for the engine
In a Ford Expedition : Bank 1 is the passenger side of the engine Sensor 1 would be close to the engine before the exhaust enters the catalytic converter ( upstream sensor )