1 Or 2 O2 Sensors?

[yitmoore]

My check engine light is on and I'm pretty sure its the O2 sensor because a
mechanic told me it would need to be replaced soon. Planning on doing it myself
but I'm confused on whether there is 1 or 2. All the parts sights say 2, but all the
service manuals only give the indication that there is 1. Have 328i, '97.

Also, do I go Bosch or NTK? $45 difference.

[mech9T8]

Actually you have 4.
2 before the cat and 2 after.
I think the 4 cylinders only have 2.

[dutchbmw]

OBDI has one O2 sensor, but yours is OBDII so you have to replace 2 sensors. I've never heard about 4 of them in a 6 banger....

[93 325i]

OBDII does have 4 O2 sensors. The 2 pre cat sensors are regulating while the 2 post cat sensors basically analyze the emissions to make sure the pre cat sensors are doing their job. This is for US versions at least, to cut back on smog levels and make the cars more "environment friendly".

[bigred318]

so which one do you have to replace when your 02 sensor goes out?

David

[kestrel325is]

Originally posted by bigred318@Jan 12 2005, 11:44 AM
so which one do you have to replace when your 02 sensor goes out?

David

[snapback]269929[/snapback]

Generally if you pull codes, it indicates which bank, and whether it's before or after the cat. Or, you could break out a multimeter and check them individually, or just replace all 4, because if one's gone bad, the rest are usually on their way.

[bigred318]

wow well i guess we learn something new each day, i thought there might be 2... but 4 that was a surprise

David

[Silverstreak]

Usually the ones that go out are after the catalytic converters.
Yes there are 4 on OBD2 and 2 on OBD1

[bkcraun]

OK, there's conflicting information on this thread regarding pre-96 OBDI E36's.
Do they have one O2 sensor or two???

[kestrel325is]

OBD I bimmers only have one sensor. Pre-cat.

[drz]

I would replace all four -- or at least a whole pair on whichever side of the cat you have a fdailure -- with Boschs.

[bigred318]

hahahha we keep jumping around with numbers research time! or autotech? where are you!! haha

David

[TECH]

A 97 model 3 series is an E36......only the E46 has 4 oxygen sensors....


When in doubt, crawl under and look.

[mech9T8]

Sorry Tech but you're incorrect.
I have a '96 328 and I have 4 O2 sensors.
O2 sensors are pretty expensive so if you replace all 4 that will cost you alot of money...even if you do it yourself.

[93 325i]

1995 and older- OBDI = one
1996 and newer-OBDII= four