i juss got a 00 si.. and it dosnet have a seconday o2 air sensor so the check engine light is always on.. how do u add the second one if thier is no harness.. and can it pass smog with the check engine light on..??

 

I don't think it will pass. The 2nd O2 sensor is there for a reason. It is probably releasing gasses at levels above passing. Why is there no harness?

 

well i didnt see a harness but ill make sure after is stops raining

 

does the si have one or 2 o2 sensor..

 

Someone correct me if I'm wrong, but I thought the Si has 2 o2's. The first is in the exhaust manifold by the collector and the second one is IN the cat. And the wires for the second o2 go up into the floor of the car behind the dash.

 

I'm not an ECU guru, but I believe OBD1 vehicles usually carry 1 O2 snesor and everything after that, being OBD2+ carry 2 sensors. 1 on the header and 1 before the catalytic converter. That's how it is on my girl's 1997 Honda Accord EX anyways, where 1994-1995 are OBD1 and 1996-1997 are OBD2.

 

well i know that accords are obd2 but i dont know if 2000 si is obd1 or obd2

 

I'm pretty sure everything 1996 and newer is OBDII

 

96-98 civics are obd2a
99-00 are obd2b
and yes the obd2a-b require 2 02 sensors.
somebody prolly put a testpipe on it. the 2nd 02 sensor plug goes through the floor in front of yer console.

 

did the car come like that? I would assume there is a harness through the firewall underneath the cat. At least the original 4 o2 sensor wires.

I believe all 96-00 carry 2 o2 sensors.

I'm going by what my 98 ex has... Just get a used OEM cat or any lagal high flow cat (carsound etc.) and also get the o2 sensor from http://www.oxygensensors.com

I think you have a high flow cat w/ no o2 sensor.