97 gsr, originally obd2 with p72. I bought the obd1 conversion harness and am now running a p28 with a crome base map. Now im curious... Does the second o2 sensor get used? If i recall, most obd1 cars use 1 o2 sensor (pre cat) where the one im curious about is the post cat or in cat o2 sensor. Heres a pic if it helps...

As you can see, i have a straight pipe on there right now and am redoing my exhaust. Im hoping i can run open header for like 2 days without that o2 hooked up OR just disconnecting it! lemme know peeps!

 

nope...OBDI only uses one. ODBII uses both.

 

thats what i was hopin for! So ill be safe to unplug the POST cat o2 (the one picture, closest to shift ****) or does obd1 use that one and NOT the pre cat o2?

 

it uses the pre cat.

I responded to the question of "Does the second o2 sensor get used"

Maybe you should learn how to put together a sentence. It took me a few reads before I understood what you were attempting to say......

 

yea, doin 50 things at once can do that to me I'll slow down, sorry man. Thanks for the help

 

It's a bit difficult to tell from the photo, but it looks as if the "test pipe" is welded directly to the exhaust manifold and to the rest of the exhaust. If that's the case, I would suggest installing some sort of flexible joint between the header and the exhaust system.

 

Yea its welded to the old stock manifold. Had a buyer for my jdm itr header so i ripped that out and just mad the stock header work. I was gonna run open header, but i figured the second o2 was neccasary, which is why i made the "Test pipe"

 

if ur running a OBD1 ECu . and u dont know which one of the 2 sensor is connected just do it by hit and try method . D/C one and see if the engine check lights comes in . if not the other must be the one which is connected .
and also it dosent matter for obd1 ecu that is conected before or after the cat . its up to you .

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by salman &raquo;</TD></TR><TR><TD CLASS="quote">and also it dosent matter for obd1 ecu that is conected before or after the cat . its up to you .</TD></TR></TABLE>

On the contrary, there is a reason why Honda placed the primary sensor before the cat. The readings will not be as accurate with the primary sensor located downstream of the cat.