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E39 (1997 - 2003) The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki
I'm thinking about replacing all my oxygen sensors; (2001 525i w/165k miles/M-54 engine type)
Getting the ses code referencing the O2 sensors/running lean that sort of thing. I had one O2 sensor replaced, "bank 2 front oxygen sensor" (what's on my invoice). Though, not exactly sure the location of this particular sensor. Meaning, I know it's one of the O2 sensors as shown in your diagram (pre-catalysts). I just don't know which one. At this point, a visual inspection they look practically the same and this was back in Nov, 2008/105K miles. As far as I know no other O2 sensors have been replaced.
So, with the mileage of the vehicle I was gonna simply replace all 4 O2 sensors, including the one replaced at 105k.
I've found a decent youtube vid that demonstrates the pre-catalysts:
Easy enough with the proper tools.
But, I have not been able to locate a decent vid for the O2 sensors (post-catalysts) underneath the vehicle. I'm a very visual type of guy. I comprehend better when I can see it...though, it sounds the post-cat O2 sensors are pretty straight forward, I just hope I can get them off.
If I can get some help with some clarifications:
In regards to the O2 sensor:
Bank 1 O2 sensor is located closest to fan?
Bank 2 O2 sensor is located closest to firewall?
(with that said, the O2 sensor I mention above that was replaced, should be the one nearest the firewall?)
I found O2 sensors on rockauto:
BOSCH Part # 13477 OE Type - Exact Fit; Heated; Wires: 4; Length (in): 12.8 One of our most popular parts Upstream; Engine Code M54 $50.79
BOSCH Part # 15109 OE Type - Exact Fit; Heated; Wires: 4; Length (in): 38.6 One of our most popular parts Downstream; Engine Code M54 $62.79
Upstream> is the sensors on top (pre-cat), engine compartment area as represented in your pic?
Downstream> is underneath the vehicle (post-cat) somewhere after the catalytic converter?
I appreciate any all help, thx.
Today, I replaced my precat O2 sensors Bank 1 and 2, not to bad. I want to tackle my post next weekend.
My question is: does the post and pre-cat O2 sensors connect to one another? And if so, I have to snake the wiring from the catalytic (below the car) to where the pre-cat O2 sensors are located?
6 Oct 2013:
I manage to replace my post-catalytic O2 sensors (downstream)
Thx to all here and a clarification post from "pshovest" I was able to change my post-cats (down-stream) with some work...liquid wrench to loosen the sensors from the exhaust definitely helps. Posted some pics for those that appreciates visuals...Also, there was mention of 'why" change out the post-cats? Well, I think its necessary. I replaced my pre-cat on 1 Sep, within a week or so my engine light returned with the P0174 code. I replaced my post-cats on 6 Oct, and though it's only been 2 weeks or so, no code. But the one thing that is very noticeable is my mileage, it has dramatically improved at least on the highway miles side. Hope this helps anyone else in my situation. Thx all, great site and drive well. Oh one other thing, when removing my sensors, one was situated sideways (easy to orient myself with the "righty-tighty/lefty-loosey" or "clock-wise/tighten", "counter-clock-wise/loosen". The other was situated on top of the exhaust. So I'm physically situated directly opposite of this sensor. So the rules are reverse when tightening and loosening this sensor. It kinda went like this: got the the sideways off first and completely replaced it. Now i'm feeling awesome. Then of course, the one situated in the opposite orientation of my physical position was not cooperating. After more spaying of liquid wrench and much swearing...and its a tight fit. I took a break, gathered my composer and got back under the car to tackle this sensor. Then it hit me, what I was doing wrong, spent about an hour trying to get it off. I was going in the wrong direction!!! Got it off and replaced it in about 30 minutes...crazy...just thought I'd share...
I was getting the running lean codes bank 1 & 2 (171 & 174). The pre-cat/Bank 2 was replaced awhile ago (about 105kmiles) but the others have not. I'm at about 166K miles, now. I changed out both the pre-cats yesterday, just looking the change out the post-cat, since I already purchased them...
Hey, "PSHOVEST"...just wanted to let you know I small bit of info helped me out alot, thx. Below is a link to my O2 sensor post, thx again..