There are 2 oxygen sensors.
A 2001 Ford Explorer Sport , with the 4.0 liter Single Over Head Cam V6 engine should have ( 4 oxygen sensors )
On a 1998 Ford Explorer Sport : If it has the 4.0 litre EFI engine ( which is an over head valve / pushrod design engine / the 8th character of the VIN is an " X " ) there are ( 3 oxygen sensors ) If it has the 4.0 litre SOHC engine ( the 8th character of the VIN is an " E " ) there are ( 4 oxygen sensors )
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 )
This is only going to answer half of the question : On a 1995 Ford Explorer , 4.0L EFI , V6 engine ( which is an Over Head Valve / pushrod design ) There are ( 2 ) oxygen sensors * I BELIEVE they are in the outlets of each exhaust manifold *
there are sensors all over the engine, transmission, chassis, etc.
The 4.0 liter OHV engine has ( 3 ) The 4.0 liter SOHC engine has ( 4 ) The front ( 2 ) oxygen sensors are used in the adjustment of the engine air / fuel ratio
My Chilton repair manual - engine wiring schematic shows ( 2 ) heated oxygen sensors for the 1993 Ford Explorer
On a 2001 Ford Explorer Sport Trac , 4.0 ( the engine oil pump is INSIDE the engine oil pan )
On a 1997 Ford Explorer / Explorer Sport : The electric fuel pump is INSIDE the fuel tank
For a 2001 Ford Explorer Sport Trac : There are ( 6 spark plugs ) for your 4.0 liter V6 engine
Bank 1 is the passenger side of the engine in your Ford Explorer
In a Ford Expedition , Ford Explorer Sport , Ford Explorer : ( bank 2 is the drivers side of the engine , whether it is a V6 or V8 engine )