Hondata

I know an 02-04 Primary O2 sensor is "needed." I have looked, and can't understand why. My friend who used to work for Acura as a tech did point out the ecu wiring for 02-04 vs 05-06 is different. I can't remember, but on one of the models, it shows the wiring for the Primary O2 sensor has one extra wire into the ecu while the other model has the wire directly connect to the Relay. According to my friend, he did try this, and was getting readings from the O2 with a K-Pro installed on his 05 Type S. He did not use an 02-04 Primary O2, he kept the stock 05 O2 installed.

Would one be able to get away with retaining the stock 05 Primary O2 sensor by running a wire to the O2 Sensor relay?

It's not clearly explained why an 02-04 Primary O2 is "required." Could this be explained?

They have the same wiring, but are different interally.

05-06 is a narrow band o2 compared to the 02-04 which is a wideband

narrow can only read about from 14-15 A/F or something like that

the 02-04 wideband can read from 11 to 32 A/F

No, both the 02-04 and 05-06 o2 sensors are cell driven widebands. They just need different driving circitry to run correctly, so must be matched to the ECU.