On a 1999 Ford Contour , 2.5 litre V6 engine :
firewall
1-----2-----3 ( Bank 1 )
4-----5-----6 ( Bank 2 )
front of vehicle > driver
Trouble code P0430 means: Catalyst System Efficiency Bank 2 Below Threshold
Code P0171 means System to lean (bank 1)
On a 1999 Ford Explorer : Bank 1 is the passenger side of the engine ( 4.0 EFI / 4.0 SOHC / 5.0 V8 )
For the 2.5L V6, it's the bank toward the front of the car.
On a 1999 Ford E-150 : For the GASOLINE engines ( V6 , V8 ,, V10 ) Bank 1 is the passenger side of the engine and bank 2 is the drivers side
Bank 1 is the passenger side of your engine on your Ford Explorer Sensor 2 is in the exhaust pipe after the catalytic converter ( downstream )
On a Ford Taurus , V6 engine : firewall 1-----2-----3 ( bank 1 ) 4-----5-----6 ( bank 2 ) front of vehicle > driver
Bank 2 is the drivers side of the engine in your Ford Expedition
P0420 Catalyst System Efficiency Below Threshold (Bank 1)
On your 1999 Ford F-150 , 4.2 liter V6 engine : The left bank is the drivers side of the engine ( or bank 2 ) The right bank is the passenger side of the engine ( or bank 1 )
bank 1 is the passenger side of the engine
On a Ford Expedition ( 4.6 and 5.4 litre V8 engines ) Bank 1 is the passenger side of the engine