I have a 98 Civic DX HB (d16y7). I put headers on this weekend. I got the original o2 primary out, but the 02 2ndary did not want to budge. I cut the wires but I drove the car without the 2ndary o2 for two days...the CEL was on all that time, assuming it was because of the 2ndary o2...I finally got a (bosch Universal - please no flames...I know...I know...go OEM - I dont have $$$). Anyway, I wired it up (i think it's right...if anyone has experience wiring these..please chime in) the CEL still was on..I checked the code...it's P0135 (heater circuit for o2 sensor 1 in bank 1). I reset the ecu (disconnected battary for 5 min) and switched the OEM with the Bosch o2 sensor and put the OEM to the 2ndary harness (basicially flip-flopped), still got the CEL P0135. I want to say that both the original OEM primary and the Universal can't be both bad because wouldn't the code reader throw both P0135 AND a P0137 (or something indicating the 2ndary o2 sensor is bad too)...it just throws the primary.

Also, when i reset the ecu, I turn the ignition to ON (but don't crank it over) and check the code reader...no codes. But when I turn the car over about a second or two, the CEL comes on and the code is P0135. I thought that the code reader will check the o2 sensor even if the car is not cranked over?

Am I missing something??? Is there a fuse or something that may be blown? Or, is there something else that I need to check? I really don't want to spend anymore money on another o2 sensor, because I'm not 100% sure that will cure my problem.

I really need your help...please advise....

my wiring...just in case you see the problem..
OEM wire-------->Bosch Universal
1) Green--------->Gray (Ground)
2) White----------> black (Signal)
3) black-----------> white (Heater)
4) black------------> white (Heater)

Thanks,

Ralph