Ok my father has a 1998 civic dx with 195k on it. the car runs like a champ. it's kicking a code for upstream 02 sensor. When getting ready to change the sensor I noticed the manifold had a crack. So long story short we changed the manifold and cat. It's all one unit, both up stream and down stream 02 sensors.

The reason for changing everything was he put around 85k to 95k in the last few years on the car and it's already apart what's another 50 bux for a sensor. Well after replacing everything very carefully we are still getting a code for up stream 02. So we swapped in 2 other brand new sensors. 1st a Bosch, the next one recommend by a buddy a Denso part number 234-4099. Still kicking the code as soon as you fire the car up.

I have no idea what to try now. I need to fix this because the car needs to pass a nys inspection..... Any help or links to the solution would be great.

 

Check fuse 15 and the fuse 15 TSB.

 

Will check fuse 15.. What's the fuse 15 tsb... I have no idea what that is?

 

Type fuse 15 TSB into Google and you find:

http://www.tegger.com/hondafaq/tsb/civic/x99-029e.pdf

 

Well it was not fues 15. Don't know what it could be.

 

Pull out your multimeter and check whether battery voltage from fuse 15 reaches the primary O2 sensor connector.

 

Did what you said everything checked out, and was working.

The ecu turned out to be bad. Got one off eBay and got a inspection.