Look on the exhaust system before and after the catalytic converter.
On the 4.0 L OHV engine - 2 oxygen sensors - and one sensor used as a catalyst monitor for catalytic converter efficiency mounted downstream of the converter On the 4.0 SOHC engine - 2 oxygen sensors and 2 catalyst monitors
There is a total of 4 oxygen sensors the 2 upstream sensors are located right below the exhaust manifold flanges and above the upstream catalytic converter.The 2 downstream sensors is located in the exhaust pipe,right behind the upstream catalyst,and ahead of the main catalyst.
two oxygen sensors for air / fuel ratio (and another two oxygen sensors that are called catalyst monitors installed downstream )
On a 1998 Ford Explorer XLT : With the 4.0 liter SOHC V6 engine ( 4 oxygen sensors , the 2 closest to the engine are used for adjusting the fuel ratio and the other 2 are catalyst monitors There are also ( 4 oxygen sensors if you have the 5.0 liter V8 engine )
There are 4 sensors, though not all of them are technically called "oxygen sensors. There are two that are upstream of the catalytic converters, one on each bank. Then, there are two more, one after each catalytic converter, that are oxygen sensors, but officially they are called catalyst monitors, because that is the job they are assigned to do. To recap, the two before the cats (or upstream), are oxygen sensors, and the two after the cats (or downstream) are catalyst moniters. Although all 4 of them are oxygen sensors, their titles are different.
My Haynes repair manual shows 2 oxygen sensors mounted between the engine and catalytic converter(s) and 2 oxygen sensors mounted after the catalytic converter(s) which are called catalyst monitors and monitor the efficiency of the catalytic converter(s) on your 1997 Explorer XLT with the 4.0 L SOHC engine
There are four oxygen sensors. Two are pre-catalyst and two are post-catalyst oxygen sensors. Basically, there is one sensor for each side of the engine in front of the catalytic converter and there are two sensors behind the catalytic converter.
You must mean Oxygen sensors. There are 2 upsteam (O2 sensors) and there are 2 downstream (catalyst moniters).
There are 2. One before the catalyst up front and one behind the catalyst.
On the 4.0 liter OHV - V6 - I believe there are ( 3 ) on a 1996 Ford Explorer 2 that are used for the air / fuel mixture that are before the catalytic converters ( upstream ) and 1 after the catalytic converters ( downstream ) that is used as a catalyst monitor
That would depend on what year of Ford Explorer and which engine you have ( my 1995 Ford Explorer with the 4.0 liter OHV , V6 engine has ( 2 oxygen sensors )
The 5.0 liter V8 has ( 4 ) oxygen sensors The 4.0 liter EFI ( which is an over head valve / pushrod design ) has ( 3 ) oxygen sensors Note: The 2 upstream oxygen sensors are used for adjusting the air / fuel ratio of the engine , the other oxygen sensor (s) are called catalyst monitors and monitor the performance of the catalytic converter(s)