Oxygen sensor question

[dddanielek]

I just removed the O2 sensors at the manifolds but forgot to mark which one plugs into which connector on the top on the engine.

Does it matter or are the specific to a side?

[wippenberg]

Is there a part number embedded on the sensor anywhere?
I know that it matters on an M5.

[ICTBMW]

it does matter since these are pre cat o2. The sensor sends signal back to other sources that treat the corresponding cylinder/injector..etc

Try tracing the wire back up the firewall and see whether the wire ends up in "bank 1" or "bank 2". Bank 1 is the one closest to the radiator (it houses cylinder 1-2-3)..etc. I would think "bank 1" connector is the closest one to the radiator along the fuel line.

[berkeleyEE]

I got this from Doug's Domain: 273643

[G. P. Burdell]

Great, thanks but which side starts with 1-3? Passanger side manifold or the driver's side manifold?
Huh? It's an inline six. Both exhaust headers are on the passenger side.

[sam316i]

Think he means downpipes, then there would be a left and right?

[rmr25]

I just did mine. The lead from the sensor bung on the rearmost header goes to the front connector atop the valve cover. Hence, the lead from the sensor in the forward header goes to the rearmost connector. When I first started the engine, it ran a little rough. But after about 6 starts it all smoothed out and now runs spot-on according to Live Data monitoring. I did my replacements one-at-a time, just to be sure I didn't mix them up.

[dddanielek]

I just did mine. The lead from the sensor bung on the rearmost header goes to the front connector atop the valve cover. Hence, the lead from the sensor in the forward header goes to the rearmost connector. When I first started the engine, it ran a little rough. But after about 6 starts it all smoothed out and now runs spot-on according to Live Data monitoring. I did my replacements one-at-a time, just to be sure I didn't mix them up.

So looks like cylinder #1 is the one closest to the fire wall and 6 is close to the rad? According the the picture above?? Could you confirm please?


Thanks

[berkeleyEE]

So looks like cylinder #1 is the one closest to the fire wall and 6 is close to the rad?

NO, cylinder #1 is at the front of the engine. See p.120-7 of your Bentley.

[dddanielek]

I just did mine. The lead from the sensor bung on the rearmost header goes to the front connector atop the valve cover. Hence, the lead from the sensor in the forward header goes to the rearmost connector. When I first started the engine, it ran a little rough. But after about 6 starts it all smoothed out and now runs spot-on according to Live Data monitoring. I did my replacements one-at-a time, just to be sure I didn't mix them up.


Looks like you did it backwards....

[rmr25]

No. All I said was: the lead from the rearmost header 02 bung goes to the front connector (Bank 1, cyls 1,2,3 as shown in the pic). I did that replacement first, just to be sure I made the correct connection. Since the sensors/leads in my car were factory original, I doubt they were in backwards. The engine idles smooth, pulls strong and shows no fault codes. What more can I say?

[dddanielek]

I got this from Doug's Domain: 273643


On my 97 328is, these banks are reversed. (confirmed with a scanner) like just like per rmr2's description.

[vap3]

for a 1997 318 IS auto m44 engine there is two oxygen sensors correct? I know modern cars have 4 but on the peklin site only lists one for before and after the CAT, is that correct?

So if I wanted to replace my oxygen sensors for preventative maintenance then I'd just get the two?

[dddanielek]

for a 1997 318 IS auto m44 engine there is two oxygen sensors correct? I know modern cars have 4 but on the peklin site only lists one for before and after the CAT, is that correct?

So if I wanted to replace my oxygen sensors for preventative maintenance then I'd just get the two?

Yours being a 4 cyl engine you probably have two. Call the dealer tomorrow and pretend you are buying O2 from them and ask how many you have just to be 100%.