I just got a JDM motor with JDM headers on it and I notice there are two o2 sensors on it. One is in front of car and its attached to one of the 4 exhaust coming out. The one ther one is at the collector where the 4 merge. The second sensor is just right before the cat. Im shocked to see two sensors. Why 2? Does anyone know? I know if its after the cat its for emission, but before....which one reads the a/f mixture???

 

I'll bet a lot of money its an EGT sensor. JDM motors only used 1 O2 sensor. Follow the wiring and it probably doesnt go anywhere.

 

well here is the deal: I have a 96 ek hatch with Im not sure what year the JDM ITR motor is. I just recently bought this car. The ECU is a P72(GSR) and both o2 sensors are connected. Right now I have an engine light ON and the code is 41. 41 is a the o2 sensor. I tested the sensor near the cat and it's good (I measured the two black wire and it read about 16ohms). The front sensor has no reading between the two black wire. If Im correct the two black wire is the heat wire. It should act like a resistor which mean it should have some resistance. The front o2 to my conclusion is bad. I think onced I fixed it, the engine light will go out. What is an EGT? Anyone else have an idea if I still have 2 o2 or just one?

 

Oh I almost forgot. Both sensors have 4 wires on it. Two black, 1 green, and 1 white.