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Pre-Cat O2 Sensors Replacement

DIY: 
60K views 46 replies 19 participants last post by  02jcrane 
#1 ·
Since I have the day off from work today, I decided to replace the pre-cat O2 sensors. I bought the sensors from Amazon. They are the exact match as the OEM ones. This job wasn't too hard to do once you removed all the cover pieces. The pre-cat sensors are a little harder to get to compare to the post cat sensors. Below are some pictures that I took so hopefully it will help others that want to tackle this job themselves versus taking it to the dealer. Enjoy

You will need a 8mm socket to remove the screws for the rear cover and a 16mm socket to remove the 5 bolts for the aluminum skid plate. For the O2 sensors, you can use a 22mm open wrench.
 

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#5 ·
No program is needed unless you have a service engine light.



Search for Bosch oxygen sensor 17051.
how about a link to the sensors on amazon

No problem. I changed them because I was getting fault code from them. As you can see from one the pictures comparing the old sensor vs new one that they are due for replacing.
thanks. Added to master DIY. It's part #2 here right?: RealOEM.com * BMW E60 M5 Lambda Probe Fixings

What prompted you to change it? Did you get a CEL?
 
#4 ·
#9 ·
Found it...looking in ISTA/D, Repair Instruction 31 10 010, it says replace screws and inserts. They are torqued initially to 56 nm and then 90deg past that. The torque table ( BMW TIS - 31 10 Front Axle Suspension ) tells you when to replace bolts (as in with new ones). That is not the exact table from ISTA, but the closest I can find online since I can't get ISTA to print yet.

Recommend any who have removed the front reinforcement plate to replace the 5) 10mm hex bolts (16mm head) part number 31106772199 and 3) 10mm inserts part number 31106779393. Found here: RealOEM.com   BMW E60 M5 Frnt axle support,wishbone/tension strut
 
#22 · (Edited)
Replace Them Clips. Seriously.

Found it...looking in ISTA/D, Repair Instruction 31 10 010, it says replace screws and inserts. They are torqued initially to 56 nm and then 90deg past that. The torque table ( BMW TIS - 31 10 Front Axle Suspension ) tells you when to replace bolts (as in with new ones). That is not the exact table from ISTA, but the closest I can find online since I can't get ISTA to print yet.

Recommend any who have removed the front reinforcement plate to replace the 5) 10mm hex bolts (16mm head) part number 31106772199 and 3) 10mm inserts part number 31106779393. Found here: RealOEM.com * BMW E60 M5 Frnt axle support,wishbone/tension strut
Today, I tried to get to one of my pre-cat O2 sensors out. However, I had to 'abort the mission' as I was not able to get my reinforcement plate off. The reason for this is that the clip inserts that Jim warned about above, the 2 installed in the motor rear cradle, were worn out. During my rod bearing replacement, the indy shop did *not* replace the bolts and inserts and the result is that the bolts now do not come out by simply turning them counter-clockwise. They keep hopping the threads, probably because they are contorted. These are only the 2 16mm bolts toward the rear of the car, not the 3 in the front. The picture below shows one of the clips (right side on frame with hole in it):

http://www.m5board.com/vbulletin/attachments/e60-m5-e61-m5-touring-discussion/159516d1341628053-pre-cat-o2-sensors-replacement-.jpg

I will get them out by applying some moderate force with a crow-bar while turning the bolts with a drill at higher speed, basically obliterating the clip and bolt(s). In fact, after some fuzzing with one of the bolts, I got it out today, but since I do not have new clips (and bolts), I would never be able to properly torque the plate (56Nm). I put the whole thing 'sorta' back together and stopped the project. Let's order these first and re-attempt next week the proper way.
 
#10 ·
quick thanks to you guys for the DIY, mind you its a bit frustrating taking the old and putting the new, area is very tight and you need to either tie the o2 wire so its compact to let you keep turning or just keep bringing the wire around like I did, holy cow so many screw just to take it out. good thing I have a compressor, but it was still tiring on the arms. wish I had a lift.

so far car started with no errors, I will drive it for a bit and see how it goes.

Big thanks to all esp Anzafin and Douglas_ngo...
 
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#11 · (Edited)
OP, thanks for the DIY. Here's what mine looked like (new, left bank and right bank). The car had been run from cold for about a minute to drive it onto the ramps so they're probably a little sootier than normal. I was getting occasional 2742 and 2748 error codes on bank 1 (which I think is the right bank as viewed from the driver's seat).

(BTW OP what happened to the rest of your undertray?!)
 

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#12 ·
I am really liking these DIY threads on this forum. :cool:
 
#15 ·
I believe I need to replace these O2 sensors.
Can anyone confirm my diagnosis? I've attached the error codes I'm getting. SES light is on. No limp mode but car is not smooth going up through the revs and doesn't feel like I have full power.
Also I suspect this is why I can't seem to break 11.3 MPG? (My right foot I'm sure has something to do with that but this seems awfully low?)

I was going to get the Bosch ones:
Amazon.com: Bosch 17051 Oxygen Sensor, OE Type Fitment: Automotive

And this tool to do it:
3/8" Offset Oxygen Sensor Wrench

Debating if replacing bolts is really necessary also?
 

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#17 ·
I don't really remember too much about doing it....which is probably a good thing as I usually remember the jobs that are terribly unpleasant. I think I did this before I got my lift too. Probably the only frustrating thing about doing O2 sensors is that the cable will have a tendency to keep re-screwing in the sensor every time you let it go so unplug the sensor first and twist the cable as you twist the sensor.
 
#19 ·
I did not heat mine but I did spray a bit of penetrating oil on them. Giving them a tap with a hammer would probably be helpful too. You are correct though if you snapped one off I really think the only way to get it out would be to pull the header off. On mine, once they were broke loose they could be turned easily by hand.
 
#20 ·
I need to replace one of my pre-cat sensors on the driver side. The OP indicated removing the underbody metal protection plate/bracket (beyond the transmission cover to get to the O2 sensor connector).

However, TIS says to remove the wheel well lining to get to the O2 from the side. Doing it this way can I avoid removing the metal underbody plate for which you need to replace a bunch of bolts? Anybody tried it this way? Just curious.
 
#23 · (Edited)
Finally Fixed

To complete the story, I finally got around to dealing with the spinning 16 mm hex bolt in the reinforcement plate under my engine. I decided to do it during the Xmas break such that I did not feel the Monday-is-coming daily driver pressure. I was not a picnic getting it out! My plan was to simply use an electrical impact wrench, apply pressure to the bolt with an object (screwdriver, etc.) and pull it out. But this was a no-go. I ended up cutting the head of the bolt off with a Dremel 1 inch cutting blade. Slowly but carefully to avoid damaging the plate and other stuff. That worked. When I got out the thread that was left in the frame, I put it in my vise and tried to turn the nut. I did not move! I was really really stuck on! No hope at all getting it out. So, really spend the few bucks, plan it out and put -new- clips and bolt in. (bolts 31106772199 x 5 & clips 3116779393 x 3) I put a bit of good grease on the bolts when I put the plate back on to avoid corrosion and make the loosening process easier in the future. 56 Nm of torque on the bolts. Here are some pictures of the bolt removal process:

The situation with the spinning bolt. I was able to take all other bolts out (despite the driver side rear bolt giving me the same trouble for a while, but with some trying it actually came out) and with enough play in the offending bolt being loose, I was able to turn the reinforcement plate such that the clip insertion access hole became accessible.



The carnage after carefully cutting the head off the bolt. The washer saved the plate! And thank God for Dremel tools and 3 diamond blades later! Note that the nut retaining pieces of the clip completely broke off! No wonder it spun.



The difference between the old clip that came out of the car and the new clips that went in. Clearly BMW made a design improvement!



The new clip installed in the frame. Note there are 3 clips as opposed the 2 I reported before! TIS showed only 2, not 3. The two rear bolts have clips and the front middle have a clip. I replied them all and used new bolts in all 5 locations for my 2008 6MT car. I say this because my bottom cover is different from the pictures above in @douglas_ngo situation. Not sure if the LCI related or SMG versus MT6.



And then finally I was able to replace the O2 sensor on the driver side. This should have taken 1 hour. LOL! Here is the old and new sensor, side by side.



I am not sure if the replacement will help my problem of a reoccurring P0114D fault. It -ONLY- happens on very long (1 hour +) drives, two in a row. Out and back, e.g. the two drive cycles that are needed to set the CEL for this fault. I haven't gotten out that far yet. (I might have to go see @jcolley next week for that purpose!) It will -not- happen on my daily commutes for months! Just long spirited drives. If not, it will be time for a smoke test, to see if we have small leaks. Or a new catalytic converter. Which really means: Straight pipe this puppy and get a tune?
 
#25 ·
47 Nm with an extension. 50 Nm without. Use anti seize.

You need somewhat specialized tools to pull this off. A long torque wrench and a crow foot to get to these puppies without taking your car completely apart. Remove the reinforcement plate under the engine. And when you put it back be sure to replace the clip nut inserts. Trust me on that one.
 
#26 ·
Gave this a shot yesterday and O2 sensor 1 ; owner 0! The driver side sensor wouldn't budge! The 22mm crowfoot wrench began to strip the sensor so I gave up before I stripped it completely.

I tried torching it to loosening it, applied WD40 and nothing.

I also tried an O2 sensor wrench and universal joints. But couldn't get a good grip with either one. The O2 sensor wrench could only get it to work with the limited space and the universal joint would simply swivel and couldn't get it to lock in position for proper leverage. :(

Feeling defeated :(. Sounded straight forward in principle. Thinking of taking it to my Indy shop for $175 in labor :(.

Any thoughts/suggestions?


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#27 · (Edited)
Auto part


This is the setup I used. I could not make it work with a universal joint, not even with a high impact edition. You can use the crow foot or an actual O2 socket tool. I believe I went back and forward between the 2 of them. I think I broke it loose with the O2 tool and then use the crow foot and my (bloody) hands to get it out (and back in). Try again and be patient. The socket will avoid the chance of stripping the O2 sensor.
 
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