civic si obd 2 witch one is the primary sensor and witch one is the secondary. one is coming from the motor area and the other from the obd 2 under the seats. i need to know because i have a code 41 and need to know witch one to change

 

The primary is the one toward the front of the car.

 

code 41 is the heater circuit in the primary(motorside) sensor.
In all likelyhood the black wires came out of the plug.

 

code 41 is not the o2 sensor what do you mean heater circuit this is obd 2 from a civic si 2000