O2 sensor responsible for P0171?

[Raimo5]

I would advise to take a moment and read through that entire article in ISTA and then also read Oxygen sensor before catalytic converter. It would give a better insight to those sensors and would also point out that you are looking at wrong sensors. Post cat sensors only measure the efficiency of cats and dont contribute to fuel trim. You need to look at pre cat sensors as these are wide band regulating probes.

Pay special attention to part that relates to reference air. You reference air ports might be plugged, post water fording.

You can see data valus if you go to ECU tree, select an ECU (DME in your case) and then press button, I think it was something like "call up ECU functions" or something on lower left corner. There you can trigger different things and view live data.

[750iClown]

Originally Posted by M_Bimmer

I'll have to hook up ISTA and try and get you a screen grab....there should be a "measurement" option....but you need to collect the real-time data from each O2 sensor while the vehicle is running, and after it's reached temperature.

My ISTA+ is an older version, so mine screen grabs may not be exactly like yours.

My main "thing" is to get to the live test screen. What I mean by that is, how do I get to the screen where I run the O2 sensor test with the car running? What is the click pathway to it, and am I not going to see this pathway if I'm not hooked up to the vehicle? I'm wondering as I use the software in the comfort of my home will I not see its full functionality without being hooked up to the vehicle?

[750iClown]

Originally Posted by Raimo5

I would advise to take a moment and read through that entire article in ISTA and then also read Oxygen sensor before catalytic converter. It would give a better insight to those sensors and would also point out that you are looking at wrong sensors. Post cat sensors only measure the efficiency of cats and dont contribute to fuel trim. You need to look at pre cat sensors as these are wide band regulating probes.

Pay special attention to part that relates to reference air. You reference air ports might be plugged, post water fording.

You can see data valus if you go to ECU tree, select an ECU (DME in your case) and then press button, I think it was something like "call up ECU functions" or something on lower left corner. There you can trigger different things and view live data.

Great info. Will look at this while having my coffee this morning.

[M_Bimmer]

https://www.youtube.com/watch?v=nCBWge_w-eQ

[750iClown]

Originally Posted by M_Bimmer

https://www.youtube.com/watch?v=nCBWge_w-eQ

I have pretty awesome news. I cleared the codes according to previous instructions. I allowed the hazard light to shut off while keeping key fob min 10 meters away (could take up to half hour to clear). I then checked fault codes and noticed there were a bunch of electrical codes, and a peculiar IBS (Intelligent Battery Sensor) fault. The wiring diagram in ISTA+ pointed to the battery area and all wires emanating from that particular IBS source having an issue. I then checked that area and noticed a purple wire with a clip attached to nothing. Funny thing, I immediately knew what was up before looking back there- I was attaching my trickle charger's alligator clip to a metal tab coming out of the positive battery terminal, and realized the purple-wire-clip belonged on there. Someone had removed it, probably my vehicle transport guy in order to charge the battery or start the vehicle.

Needless to say, I attached the wire, CEL disappeared, and I drove the car for like 35 minutes and had it at operating temp for at least 30 mins, drove straightaways for several minutes at 40-50 mpg, and no CEL! I am pretty pumped. See image below.

[M_Bimmer]

Originally Posted by Raimo5

I would advise to take a moment and read through that entire article in ISTA and then also read Oxygen sensor before catalytic converter. It would give a better insight to those sensors and would also point out that you are looking at wrong sensors. Post cat sensors only measure the efficiency of cats and dont contribute to fuel trim. You need to look at pre cat sensors as these are wide band regulating probes.

Pay special attention to part that relates to reference air. You reference air ports might be plugged, post water fording.

You can see data valus if you go to ECU tree, select an ECU (DME in your case) and then press button, I think it was something like "call up ECU functions" or something on lower left corner. There you can trigger different things and view live data.

Thanks for the correction...the post O2 is merely used for monitoring the CAT itself...and pre-CAT is for fuel trim....

[M_Bimmer]

Originally Posted by 750iClown

I have pretty awesome news. I cleared the codes according to previous instructions. I allowed the hazard light to shut off while keeping key fob min 10 meters away (could take up to half hour to clear). I then checked fault codes and noticed there were a bunch of electrical codes, and a peculiar IBS (Intelligent Battery Sensor) fault. The wiring diagram in ISTA+ pointed to the battery area and all wires emanating from that particular IBS source having an issue. I then checked that area and noticed a purple wire with a clip attached to nothing. Funny thing, I immediately knew what was up before looking back there- I was attaching my trickle charger's alligator clip to a metal tab coming out of the positive battery terminal, and realized the purple-wire-clip belonged on there. Someone had removed it, probably my vehicle transport guy in order to charge the battery or start the vehicle.

Needless to say, I attached the wire, CEL disappeared, and I drove the car for like 35 minutes and had it at operating temp for at least 30 mins, drove straightaways for several minutes at 40-50 mpg, and no CEL! I am pretty pumped. See image below.

Although not very explainable....that is great news! The IBS was going to be the next thing to address, but you beat us to it ....still puzzled how that purple wire would cause the CEL to light up....

[M_Bimmer]

Originally Posted by 750iClown

T....Also, where are the MAF sensors, as well as PCV? Let me know if you know that.

Cleaned off my MAFs because of a faulty PCV, so lots of oil in the intake area, so much it leaked back into the intake filters, using CRC MAF sensor cleaner, and now my N63R is purring.....love this engine!

I have a pre-LCI G12 N63, which has two MAF sensors just aft the intake filters. Your LCI G12 N63 is a different animal, and I could not find any MAF sensor on your intakes, only a temp sensor. TIS eludes that you have MAF's, but I could not confirm this in any other documentation.

Maybe someone that has an LCI G12 N63 can weigh in...

[750iClown]

Originally Posted by M_Bimmer

Although not very explainable....that is great news! The IBS was going to be the next thing to address, but you beat us to it ....still puzzled how that purple wire would cause the CEL to light up....

I spoke too soon, P0171 is back. I drove it tonight and it came back on right after starting. Back to square one. Any advice?

[M_Bimmer]

Originally Posted by 750iClown

I spoke too soon, P0171 is back. I drove it tonight and it came back on right after starting. Back to square one. Any advice?

Read the codes, clear the codes, and then post the codes that remain....the IBS should be gone now....let's go from there.

[750iClown]

Originally Posted by M_Bimmer

Read the codes, clear the codes, and then post the codes that remain....the IBS should be gone now....let's go from there.

Will do tomorrow. When you clear the codes, what do the remaining codes or the ones that do not get erased indicate? Conversely, what do the ones that got erased indicate?

[750iClown]

Originally Posted by M_Bimmer

Read the codes, clear the codes, and then post the codes that remain....the IBS should be gone now....let's go from there.

I am just hoping I can fix this on my own. Taking it to BMW to fix this is not out of the question, as I am doing quite well financially, not an issue at all, but I am very mechanically inclined and would hate to give BMW open season with their labor rate at $175 per hour. I have fixed major issues on all my vehicles, but BMW is a new beast all together. I need to tackle this and learn my new vehicle. I hope we can nail this down, would be so rewarding.

[Raimo5]

Originally Posted by 750iClown

Will do tomorrow. When you clear the codes, what do the remaining codes or the ones that do not get erased indicate? Conversely, what do the ones that got erased indicate?

Clearing the codes gets rid of old and useless ones. It's basically decluttering the hit list and to see what immediately pops back up so we can focus on those.

To be honest, I dont know if ISTA will run a vehicle check after codes are deleted. Once the PAD mode is reactivated, it only takes seconds to finish the operation which makes me think that complete vehicle check is not automatically performed. Might be worthwhile to press that button so ISTA will run or trigger self diagnosis on all the modules.

Mixture control codes can be trickier as these might only pop up during operation. Permanent SAE codes wont be cleared before root issue is rectified, system passes self diagnosis and initiates healing counter.

Originally Posted by 750iClown

I am just hoping I can fix this on my own. Taking it to BMW to fix this is not out of the question, as I am doing quite well financially, not an issue at all, but I am very mechanically inclined and would hate to give BMW open season with their labor rate at $175 per hour. I have fixed major issues on all my vehicles, but BMW is a new beast all together. I need to tackle this and learn my new vehicle. I hope we can nail this down, would be so rewarding.

I hear you mate. I like to do all the work I can do myself as well. It gives you great insight to vehicle and helps you better understand operational characteristics and faults in the future.

[750iClown]

Originally Posted by Raimo5

Clearing the codes gets rid of old and useless ones. It's basically decluttering the hit list and to see what immediately pops back up so we can focus on those.

To be honest, I dont know if ISTA will run a vehicle check after codes are deleted. Once the PAD mode is reactivated, it only takes seconds to finish the operation which makes me think that complete vehicle check is not automatically performed. Might be worthwhile to press that button so ISTA will run or trigger self diagnosis on all the modules.

Mixture control codes can be trickier as these might only pop up during operation. Permanent SAE codes wont be cleared before root issue is rectified, system passes self diagnosis and initiates healing counter.



I hear you mate. I like to do all the work I can do myself as well. It gives you great insight to vehicle and helps you better understand operational characteristics and faults in the future.

Definitely. I just finished testing with ISTA+, and here are screen grabs of the codes before deleting fault memory. I am erasing from fault memory now. Will post that screen grab in next post.

[750iClown]

Originally Posted by Raimo5

Clearing the codes gets rid of old and useless ones. It's basically decluttering the hit list and to see what immediately pops back up so we can focus on those.

To be honest, I dont know if ISTA will run a vehicle check after codes are deleted. Once the PAD mode is reactivated, it only takes seconds to finish the operation which makes me think that complete vehicle check is not automatically performed. Might be worthwhile to press that button so ISTA will run or trigger self diagnosis on all the modules.

Mixture control codes can be trickier as these might only pop up during operation. Permanent SAE codes wont be cleared before root issue is rectified, system passes self diagnosis and initiates healing counter.



I hear you mate. I like to do all the work I can do myself as well. It gives you great insight to vehicle and helps you better understand operational characteristics and faults in the future.

Here is what's left after deleting fault memory:

[750iClown]

Originally Posted by M_Bimmer

Read the codes, clear the codes, and then post the codes that remain....the IBS should be gone now....let's go from there.

Good morning. Any ideas based on my screen grabs?

[750iClown]

Originally Posted by Raimo5

Clearing the codes gets rid of old and useless ones. It's basically decluttering the hit list and to see what immediately pops back up so we can focus on those.

To be honest, I dont know if ISTA will run a vehicle check after codes are deleted. Once the PAD mode is reactivated, it only takes seconds to finish the operation which makes me think that complete vehicle check is not automatically performed. Might be worthwhile to press that button so ISTA will run or trigger self diagnosis on all the modules.

Mixture control codes can be trickier as these might only pop up during operation. Permanent SAE codes wont be cleared before root issue is rectified, system passes self diagnosis and initiates healing counter.



I hear you mate. I like to do all the work I can do myself as well. It gives you great insight to vehicle and helps you better understand operational characteristics and faults in the future.

Good morning. Any ideas based on my screen grabs?

[Raimo5]

Seeing as you are running lean on both banks, I would check fuel pressures and if everything is okay there, start inspecting parts visually. Either you get too much unmetered air or there is not enough fuel delivered, or both banks have it's regulating loops ruined by water ingestion or other reasons.

[750iClown]

Originally Posted by Raimo5

Seeing as you are running lean on both banks, I would check fuel pressures and if everything is okay there, start inspecting parts visually. Either you get too much unmetered air or there is not enough fuel delivered, or both banks have it's regulating loops ruined by water ingestion or other reasons.

The code in OBD2 indicates that only bank 1 has the issue as far as I saw in the OBD2 code reader. Are you saying that 118100 and 118101 indicate its both banks? If so, can I use the software to check fuel pressure? Maybe "text search" will yield an ISTA test procedure for that idk. At what point, aside from visual inspection, will I need additional tools to test components relevant to this issue?

Also, you or someone else said they couldn't see a MAF sensor anywhere on my beast in the engine pics I attached. Is that true? I would love to find the MAF sensors if they exist and start there with a good MAF sensor cleaning.

[M_Bimmer]

Originally Posted by 750iClown

IMG]https://www.dropbox.com/scl/fi/07p36ddlc8khc1a1dgwo2/ISTA_01012024_AfterFault_B.JPG?rlkey=vg5ql2n2bd69k 7zyjollg8x87&raw=1[/IMG]

If you pop your trunk, and access your battery compartment, there should be an aerial module mounted just in front of the battery...is it plugged in? If you address this module, your 2nd code may go away.

In the off chance that I miss guided you, feel free to select the code set in ISTA and run the Test Plan against that code.

I circled the rear aerial in the photo:

[M_Bimmer]

Originally Posted by 750iClown

Here is what's left after deleting fault memory:

Did you drive around after clearing the "soft" codes? And these are the only two "hard" codes left?

BTW, I'd pull the negative terminal on your battery, let it sit for a few minutes, then reconnect the ground wire to the battery. Run ISTA, clear all the codes. Take the car for a short spin, then post the BMW version of the emission codes.

[750iClown]

Originally Posted by M_Bimmer

If you pop your trunk, and access your battery compartment, there should be an aerial module mounted just in front of the battery...is it plugged in? If you address this module, your 2nd code may go away.

In the off chance that I miss guided you, feel free to select the code set in ISTA and run the Test Plan against that code.

I circled the rear aerial in the photo:

I planned to open the trunk today and look around for anything else unplugged but got busy. I'll check when I get home tonight. I'm looking forward to running test plans on these existing codes. Thanks so much for the pic and tips. This is a vehicle worth $95k pre-issue. I was going to get one without issues but saw this. So far I am feeling great about this purchase and got a steal, just need to nail down this lean-mixture issue.