O2 sensor responsible for P0171?

[750iClown]

Hi all. 2022 750i xDrive. I'm getting a P0171 bank 1 code. I realize it could be caused by an air leak, possible MAF sensor, or the PCV valve could be the cause as well as clogged fuel injector(s) or some sort of fuel sending problem. I get all that, but my question at this point is, where is the O2 sensor that's throwing this code located exactly? Thanks for your help.

[M_Bimmer]

Isn't your vehicle still under warranty or at least emissions warranty?

To answer your question, your Lambda sensors (or probes) are located center of your engine, underneath the air intake assembly shown below.

Typically your pre-CAT 02's should be steady voltage (readable through most OBDII scanners), while the post-CAT 02's provide the fuel trim feedback to the ECU's and typically the ones that are issues (although rarely, the pre-CAT's cause emission codes to be set).

You have two pre-CAT Lambda and two post-CAT Lambda sensors.

You should really use data to determine your OBDII Emissions code by pulling the BMW codes too.

[750iClown]

Originally Posted by M_Bimmer

Isn't your vehicle still under warranty or at least emissions warranty?

To answer your question, your Lambda sensors (or probes) are located center of your engine, underneath the air intake assembly shown below.

Typically your pre-CAT 02's should be steady voltage (readable through most OBDII scanners), while the post-CAT 02's provide the fuel trim feedback to the ECU's and typically the ones that are issues (although rarely, the pre-CAT's cause emission codes to be set).

You have two pre-CAT Lambda and two post-CAT Lambda sensors.

You should really use data to determine your OBDII Emissions code by pulling the BMW codes too.

This vehicle is no longer under warranty as it had a water salvage issue, but it is in brand new condition. The water came in thru intakes but was drained and i changed spark plugs and one coil that was at issue and it runs perfect aside from this P0171 code. I changed air filters as well. I just need to find where this code is being caused. My question about the pre-cat lambdas... do they have to be accessed from under the vehicle at the front of the engine? I looked this morning and can't see them from the top of the engine view.

[M_Bimmer]

Well, that's new info....

Any chance you can borrow or pick up a scanner that would provide BMW codes on top of the OBDII Generic code?

If you don't have ISTA (highly recommended), then a Foxwell NT530 would suffice....

Hopefully you don't have a partially plugged cat.

[750iClown]

Originally Posted by M_Bimmer

Well, that's new info....

Any chance you can borrow or pick up a scanner that would provide BMW codes on top of the OBDII Generic code?

If you don't have ISTA (highly recommended), then a Foxwell NT530 would suffice....

Hopefully you don't have a partially plugged cat.

I ordered an OBD2 scanner but in the meantime ran one at Auto Zone. See results in the pic link below. That is a pic of the code found there P0171 along w some "secondary codes" (I think).

https://photos.app.goo.gl/XLjR48FL89ynNFtB7

[M_Bimmer]

Originally Posted by 750iClown

I ordered an OBD2 scanner but in the meantime ran one at Auto Zone. See results in the pic link below. That is a pic of the code found there P0171 along w some "secondary codes" (I think).

https://photos.app.goo.gl/XLjR48FL89ynNFtB7

You should really get a hold of a BMW code reader, which will also read generic OBD II codes, which Autozone pulled for you....you need the BMW codes.

Based on on your secondary codes, I would not assume your Lambda sensor is an issue...not just yet.

[750iClown]

Originally Posted by M_Bimmer

You should really get a hold of a BMW code reader, which will also read generic OBD II codes, which Autozone pulled for you....you need the BMW codes.

Based on on your secondary codes, I would not assume your Lambda sensor is an issue...not just yet.

Yea I had the car go thru BMW dealership service after I got it. Threw in new spark plugs and it needed #7 Ignition coil. After that runs perfect but CEL came up w these codes. I told them for the time being I'll take it and see if I can tackle it. Could be something simple. What additional information can a BMW code reader provide?

[M_Bimmer]

Originally Posted by 750iClown

Yea I had the car go thru BMW dealership service after I got it. Threw in new spark plugs and it needed #7 Ignition coil. After that runs perfect but CEL came up w these codes. I told them for the time being I'll take it and see if I can tackle it. Could be something simple. What additional information can a BMW code reader provide?

The Foxwell NT530 provides almost the exact "text" menu version of ISTA (which is windows based)....some of the aftermarket tablet BMW code reader do a good job of emulating ISTA, but ISTA (including the free version) provides troubleshooting test plans for each BMW code that is set...ISTA also allows remote exercising and data readouts from most items that are under test.

In your case, it would be very beneficial to download ISTA+ for free or get a preinstalled HDD off of eBay.

[750iClown]

Originally Posted by M_Bimmer

The Foxwell NT530 provides almost the exact "text" menu version of ISTA (which is windows based)....some of the aftermarket tablet BMW code reader do a good job of emulating ISTA, but ISTA (including the free version) provides troubleshooting test plans for each BMW code that is set...ISTA also allows remote exercising and data readouts from most items that are under test.

In your case, it would be very beneficial to download ISTA+ for free or get a preinstalled HDD off of eBay.

Ok I'll need to get the NT530 and start there.

[M_Bimmer]

Originally Posted by 750iClown

Excellent information. Question, when i download ISTA+ to my laptop what cord do I need to interface the laptop to the vehicle? One end w a USB connection to PC and the other end OBD2 connection?

Laptop to vehicle connection can be done wired through a ENET to USB cable, or through a wireless USB tranceiver to a bluetooth wireless ENET dongle.

I typically use the ENET cable like this one...but get one that is priced for your budget and long enough so you can use you laptop outside of the car.

[750iClown]

Originally Posted by M_Bimmer

Laptop to vehicle connection can be done wired through a ENET to USB cable, or through a wireless USB tranceiver to a bluetooth wireless ENET dongle.

I typically use the ENET cable like this one...but get one that is priced for your budget and long enough so you can use you laptop outside of the car.

Excellent I'm going to look into this tmrw.

[750iClown]

Originally Posted by M_Bimmer

Laptop to vehicle connection can be done wired through a ENET to USB cable, or through a wireless USB tranceiver to a bluetooth wireless ENET dongle.

I typically use the ENET cable like this one...but get one that is priced for your budget and long enough so you can use you laptop outside of the car.

So to clarify, i don't need to get the Foxwell scanner if I download ISTA to my computer and interface to the car w that cord you sent the link to?

[M_Bimmer]

Here is the ECU Tree on my G12 after registering the new battery in the trunk today....replaced all the air filters (cabin & engine), and plan to do the spark plugs before the new year.

[M_Bimmer]

Originally Posted by 750iClown

So to clarify, i don't need to get the Foxwell scanner if I download ISTA to my computer and interface to the car w that cord you sent the link to?

If you get ISTA and the ENET cable, you should be good to go....I own a Foxwell NT530 for my BMW as backup, and my Porsche 911 991.1 C2S Cab

[750iClown]

Originally Posted by M_Bimmer

If you get ISTA and the ENET cable, you should be good to go....I own a Foxwell NT530 for my BMW as backup, and my Porsche 911 991.1 C2S Cab

Awesome. Ordering the cord now. I'm the guy in the movie theater using his phone lol. Albeit very dim screen. The Iron Claw, very good flick, highly recommend.

[750iClown]

Originally Posted by M_Bimmer

Here is the ECU Tree on my G12 after registering the new battery in the trunk today....replaced all the air filters (cabin & engine), and plan to do the spark plugs before the new year.

Awesome. Thanks so much for all this information. Great board!

[750iClown]

Originally Posted by M_Bimmer

Laptop to vehicle connection can be done wired through a ENET to USB cable, or through a wireless USB tranceiver to a bluetooth wireless ENET dongle.

I typically use the ENET cable like this one...but get one that is priced for your budget and long enough so you can use you laptop outside of the car.

Is this the same cord? Looks like it and it's much cheaper.

https://www.amazon.com/Ethernet-Inte...s%2C334&sr=8-3

[M_Bimmer]

Originally Posted by 750iClown

Is this the same cord? Looks like it and it's much cheaper.

https://www.amazon.com/Ethernet-Inte...s%2C334&sr=8-3

That should work.

[Raimo5]

Just make sure you get RJ45 to USB adapter in case your laptop has no ethernet port. These days, most dont. Cheap and expensive cables are all the same. There are no control electronics inside those things, and have a straight wire connection for 6 wires and a resistor between pins ... I cant remember. Just get a cheap one - everything above that is a markup.

And ISTA will also provide you with service manuals, so that would be the route to go for one shop solution. From there on, you can get familiar with ESYS and others, as ENET cable will allow you to use them all.

Also, if water came in thru intake, then MAF sensors can also be damaged. They are pretty precise units and run self diagnostics, but I have seen many cases where they are still within tolerance spec so's not to trigger CEL, but inaccurate enough to start causing mixture issues. Again, it would require electronic diagnosis to pinpoint the issues and give further information.

[750iClown]

Originally Posted by Raimo5

Just make sure you get RJ45 to USB adapter in case your laptop has no ethernet port. These days, most dont. Cheap and expensive cables are all the same. There are no control electronics inside those things, and have a straight wire connection for 6 wires and a resistor between pins ... I cant remember. Just get a cheap one - everything above that is a markup.

And ISTA will also provide you with service manuals, so that would be the route to go for one shop solution. From there on, you can get familiar with ESYS and others, as ENET cable will allow you to use them all.

Also, if water came in thru intake, then MAF sensors can also be damaged. They are pretty precise units and run self diagnostics, but I have seen many cases where they are still within tolerance spec so's not to trigger CEL, but inaccurate enough to start causing mixture issues. Again, it would require electronic diagnosis to pinpoint the issues and give further information.

I ordered the cord in the link I posted last night. $14. I'm excited to receive it on the 28th and to try out this ISTA software. Regarding MAF sensors I was actually under the hood looking for them yesterday. I didn't immediately see them on the air intake tubes after the air filters. Gotta be somewhere around there but surprisingly not easily seen. I was watching YouTube vids on cleaning MAF sensors with MAF sensor cleaner. That is the first thing I want to try even without looking into the codes any further.

I got a good deal on this vehicle which pushed me into it, but still paid a good chunk of money. I was going to get a 7-Series either way but I came across this, no water in interior, absolutely mint inside and out, a beauty. I figured I'd asses the engine and go from there with a lot of wiggle room to get it to 100% operation. All it needed was 1 coil, spark plugs, and addressing this issue. Vehicle has book value of $94k.

[M_Bimmer]

Take your engine cover off the top, snap a picture and post....I'll draw a line where the Lambda senor pre-cat's are.....the post-cat requires you to remove the intake filter housing and plenum off the rear of the engine to get to the wires and sensor, but if you take this assembly off and take a picture, I can draw another line where the post-cat Lambda sensor is located.

BTW, to take off the intake filter assembly from the engine, it's easy. Loosen the intake plenum pre-filter (there should be two large hose clamps - just loosen one on each side of the engine). Lift up on the rear of the complete assembly - this is the hardest part as there is a heat shield mounted on the underside of the air boxes to protect them from the CAT's.

The airboxes sit on 4 mounts similar to your engine cover, but only larger.

You need to tilt the rear of the air box assembly toward the front of the vehicle first to clear the cowling. then disconnect the intake tubes...then it should just lift out.

A PITA the first time you do it...it will take you 2 minutes every time afterwards.

Note: If you need TIS documentation (included with ISTA) between now and getting your ISTA version running, I can provide.

[750iClown]

Originally Posted by M_Bimmer

Take your engine cover off the top, snap a picture and post....I'll draw a line where the Lambda senor pre-cat's are.....the post-cat requires you to remove the intake filter housing and plenum off the rear of the engine to get to the wires and sensor, but if you take this assembly off and take a picture, I can draw another line where the post-cat Lambda sensor is located.

BTW, to take off the intake filter assembly from the engine, it's easy. Loosen the intake plenum pre-filter (there should be two large hose clamps - just loosen one on each side of the engine). Lift up on the rear of the complete assembly - this is the hardest part as there is a heat shield mounted on the underside of the air boxes to protect them from the CAT's.

The airboxes sit on 4 mounts similar to your engine cover, but only larger.

You need to tilt the rear of the air box assembly toward the front of the vehicle first to clear the cowling. then disconnect the intake tubes...then it should just lift out.

A PITA the first time you do it...it will take you 2 minutes every time afterwards.

Note: If you need TIS documentation (included with ISTA) between now and getting your ISTA version running, I can provide.

Thank you so much. I will definitely be in touch and i will post photos soon. Looking forward to your feedback. Merry Christmas.