both sides you need to know which bank you are working on the scanner should have said something like bank 1 sensor 1 or bank 1 sensor 2 a bank is a side of the motor bank 1 is the side with cylinder #1 and the the other side is bank 2 if it is sensor 1 then that is before the catalytic converter if it sensor 2 then it is after the cat. hope that helps
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 )
On a 2000 Ford Expedition ( 4.6 and 5.4 ) Bank 2 is the drivers side of the engine Sensor 1 is close to the engine BEFORE the exhaust enters the catalytic converter
Bank 2 is the drivers side of the engine Sensor 2 is in the exhaust after the catalytic converter ( downstream )
On a Ford Expedition , 5.4 and 4.6 Bank 2 is the drivers side of the engine Sensor 2 is in the exhaust AFTER the catalytic converter ( downstream sensor also called the catalyst monitor )
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 )
On a Ford Expedition ( 4.6 and 5.4 ) Bank 1 is the passenger side of the engine Sensor 1 would be close to the engine BEFORE the exhaust enters the catalytic converter Sensor 2 would be AFTER the exhaust has passed through the catalytic converter
On a 1998 Ford F-150 or Ford Expedition , 5.4 Bank 2 is the drivers side of the engine Sensor 1 would be close to the engine BEFORE the exhaust enters the catalytic converter
under the intakemanifold on the passenger side
Bank 2 is the drivers side of the engine in your Ford Expedition Sensor 1 is in the exhaust BEFORE it enters the catalytic converter ( upstream )
Bank 2 is the drivers side of the engine in a Ford Expedition Sensor 2 is after the catalytic converter ( downstream )
Bank # 1 is the passenger side of the engine in a Ford Expedition Sensor # 1 would be before the catalytic converter ( upstream sensor ) Sensor # 2 would be after the catalytic converter ( downstream sensor )
Bank 1 is the passenger side of the engine in your Ford Expedition Sensor 2 is after the catalytic converter ( downstream )