Ultragauge + Scangauge on an obdii y cable
 

I just wanted to put this here to save another the trail and error I just went through.

I cut off a second obdii port from another civic and spliced it to my existing one.

I confirmed that on a 1997 Civic you CANNOT run both gauges at the same time.

I have read that others were successful doing this but it definitely doesn't work with this ecu.

I'm pretty certain it's due to the K-line ISO 9141 protocol this car uses.

I bet if your car uses a can-bus it would work.