Help! which O2 sensors? bosch but?# of wires?

Looking at ads for aftermarket O2 sensors, Some have good sales today for fathers day,but they often list multiple choices., even by Bosch. I have learned that part of the difference is whether
the sensor comes with a BMW electrical fitting. I am happy to splice the old fitting to save
$40-60 x4.
But they ask two wire, three wire or four?
Does anybody know the difference? Are post and pre cat the same?
I have e39 01 and a 99 323, basically the m52tu and m54, same as a 330i.
Anybody know the big picture on these??
Or just where to get best price?
thanks

You have 4 wire. The generic Bosch ones work.
For the wires:
White - Heating element
White - Heating element
Black - Signal
Grey - Ground

I've installed the generic ones on various cars (even BMW's) and have never had a problem.

Perfect, thanks.
I loooked them up on three popular sources and did see a pattern. The wire length was also a clue. Looking only at ones
Claiming to be Bosch. I found one with 320mm intake I believe, usually more expensive, and the 990mm exhaust. Plus the Bosch
universal 4 wire always described as premium waterproof, heated etc, although sometimes it was a little more.

Anyway the dealer wants $150-200 x 4, and I ordered with 20% off fathers day sale from car parts wholesale for $57-59
each minus 20%! so four cost less than a third as much.(less than 200 delivered)
We will see, but your comment is exactly what I wanted to know.
Is this site great or what?

Can you send me a link to where you bought those? $60 is the cheapest price I've seen for O2 sensors.

Sure.
It was carpartswholesale.com
I ordered these parts at midnight monday nite cause they had a 20% off one day sale. Well they arrived
today at noon! 36 hrs!
Turns out they are twenty minutes away form me in DFW. At least these parts shipped from there.
Anyway, they have a 15% sale now til june 22 use "thanksdad" coupon code.
here is my invoice. The sensors came to like $47 after the discount Ill post what they look like.And a graf water pumpfor $60-12.They had other brands)
I also ordered cam pos sensors.(Febi brand) they were $62 and 92 before discount. The car cover was excluded(there iist a list of excluded vendors)
I'll post pics in a few days. Its funny I would order from unproven source. I am about to do a post about
counterfeit, bad parts I bought on here from a member!

Cool, thanks! Post a review if you get a chance.

well the parts arrived as I said
here are somepics
The packaging certainly looks genuine, the positions sensors are Febi/bilstein
and the part itself is so labeled.
The Bosch stuff has some numbers but no discernable Bosch stamp?
It looks like the electrical fittings are P&P
that is the Graf water pump
Pretty blue box but no a single mark of any knid on the pump,
which feels wonderful, I mean tight smooth well machined etc,
but not a number or nothing
? normal anybody bought a Graf pump(Ive seen the name on pumps at one of the regular places like bav auto or similar) and can tell us whether theyare stamped Graf?
the pump was like $49 THE POSITION SENSORS WERE 63 AND $93 after discount

I just got some bosch 02 sensors with a part # of 13477. Were the wires long enough or did you have to extend them? They are only like 12" long. Every other pic I've seen the O2 sensor wire is about 3' long.

BTW, I got my O2 sensors from socalmotorsports on ebay. $140 shipped for a pair of pre-cat ones.

ttt

Why not just order the correct O2 sensors from bosch? I found them on amazon for under $60 and I haven't had a problem with them and it has been months.

What was the Bosch part # that you ordered?

I have a similar problem,but mine on the N42b20 4 cyslinder pre cat o2 sensor has 5 wire!!anyone with an idea where i can get these?