after i installed my greddy im getting P0140 code.
Haynes book says: downstream oxygen sensor high voltage fault.
i did some reaserch here and i couldn find anythink about that code in 4th gen maxima only 5th cali spec. mine is federal.
did i f....ed my o2 when i was installing my catback??

 

downstream O2 sensor is the one after the catalytic converter...

You might have damaged it during the install.

 

is there any way that is connected incorectly??

 

not likely - unless you broke a wire or pulled a wire out of the connector...

 

i will check it.

thank. i was confused because in 5th gen maxima P0140 – Heated Oxygen Sensor malfunction Sensor 2 Bank 1

 

I have that code also and i don't have a O2 in my cat....

 

Maybe you have the code because the o2 sensor is missing...

I believe EVERY 4th gen is supposed to have a post-cat o2 sensor. It doesn't do much (unless both front o2 sensors are not working)...

 

in my 99 max O2 sensor is behind cat

 

nope not cali-spec cars

 

all 4th gens have at least 2......downstream is on or after the cat....and it is the same code for 5th gens....the heated part des not mean anythign teh oxygen sensor is still bad in the back....the heated part is that the 02 sensors heat themselves up.....bank 1 is teh side that cylinder #1 is on, and sensor 2 is downstream