ATS*Mark

the secondary is the one thats in the cat correct , is this true for all cars , im trying to order a primary o2 for my 99 civic cx , and they go by front or rear sensor.... since the cat is part of the exhaust manifold im asuming the rear is the primary. any help would be appreciated , thanks

Jesse 99EK

They go in order starting closest to the exhaust ports.

The sensor on top of the CX manifold would be the primary, and the sensor futher down on the manifold would be the secondary.

ATS*Mark

but i thought the secondary was in the cat because the secondary only monitered cat efficiency.....

ATS*Mark

bump cause i need to know im buying one this weekend

97mini-me

The secondary o2 just lets the ecu know that your cat is doing its job. It isn't really important, but I would get one just because it is supposed to be there.

2trix

doesnt matter which one you order....their the same part #...

H_doubledeuce_A1

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hella_JDM &raquo;</TD></TR><TR><TD CLASS="quote">the secondary is the one thats in the cat correct , is this true for all cars , im trying to order a primary o2 for my 99 civic cx , and they go by front or rear sensor.... since the cat is part of the exhaust manifold im asuming the rear is the primary. any help would be appreciated , thanks</TD></TR></TABLE>

Only for OBD2 cars, OBD1 only has one the connects to the Exhaust Manifold, and I do believe that OBD0 does not have an O2 sensor.

ATS*Mark

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2trix &raquo;</TD></TR><TR><TD CLASS="quote">doesnt matter which one you order....their the same part #...</TD></TR></TABLE>

no there not , they are different prices and different part numbers.

im not asking whether or not i need a secondary , im ordering from prostreetonline.com and they sell by front and rear o2..... well the cx has the cat in front and i need to know if thats the primary or secondary.

2000blackgsr

You still have 2 o2 sensors. The first one on the manifold is the primary, the second one is the secondary. The cat is part of the manifold and the secondary will go into the cat. Hope that made sense.

ATS*Mark

no it doesnt make sence , because the first one goes into the cat...... so the secondary is the more foreward one correct?

2000blackgsr

The primary is the one closest to the engine, secondary is in the cat.

ATS*Mark

ok , well the cat is closer to the engine on the d16y7 . the cat is part of the exhaust manifold . there is one in the cat then one after the cat

@ries

OK... the one that is closer to the cylinder-head is the <U>primary</U> O2... the next O2 after that is the <U>secondary</U> O2. I hope that helps. Maybe we need a picture.

ATS*Mark

thanks emo , see i was always under the asumption that the secondary only monitered the cat so i figured it was always in the cat.....but i knew the primary was before the secondary so i kinda confused myself.

B18C1 '96 Coupe

oK MAN THIS IS SIMPLE LOOK AT YOU MANIFOLD AND PIPES. cOMING OUT THE ENGINE. tHE FIRST ONE YOU SEE NO MATTER WHAT IS PRIMARY. sECOND ONE YOU SEE IS SECONDARY. nO MATTER WHERE THEY ARE LOCATED.

sorry for yelling I didnt know mny caps was on and I am too lazy to retype.

Turbo E

make sure you buy OEM and not some craptastic "universal" O2

Smith Wise

with the exhuast manifold containing the cat converter as well, the location of the sensors are as follows...

standing directly in front of the hood...

the primary is in the upper part of the exhaust manifold...

the secondary is in the bottom part of the exhaust manifold just after the cat...

they are different, people will try to tell you otherwise, but they are different. one has a male connector, and the other has a female connector, i forget which is which...

good luck...