P2096 - Emissions Warning - Post Cat

[donsrno1]

I got a Service Engine Soon/CEL light at the weekend, along with an 'Increased Emissions' warning on the display unit. I've pulled the code and it said:

P2096 - Post Catalyst Fuel Trim System, Too Lean Bank 1 (More details for code here)

So, I've got a few questions:

1. Is it safe enough to drive the car like this, or are there any significant risks of damage etc. from driving? or does the engine drop to limp mode before any serious damage could be done?
I called my service advisor at BMW who said just to drive it till I could bring it in (this would be minimum 400 miles - I'm currently away from home with no BMW dealerships, or garages I would want to use within 100+ miles). However, I'm not entirely sure I trust his judgement from previous experience and want a second opinion. He essentially said if it was serious enough that I shouldn't drive, it would turn the SES light red and start flashing at me.

2. What are the likely outcomes, and are there any checks I can do myself before driving much or taking to dealership/garage?
(I've read process is basically to check for exhaust/vacuum leaks, then check o2 sensor after cat, and if it seems ok replace the pre-cat o2 sensor). However, is there any of that I can do without any major tools, or by buying any fairly cheap items? (I'll check for leaks, but more interested in checking o2 sensors as I've never done it before)

3. The dealership recently removed my DCT transmission to fix a leak, then reinstalled it (all under warranty). Is there anything in this process that could have lead to the issue?

Any help appreciated. I'm reading old posts now to try and understand the control system used a bit better, but I'm on a time crunch and need to decide by tomorrow evening if I can drive the car the 400 miles home.

Also - no mod's on the car (past or present) that I am aware of. If there are any discrete mods which could cause the issues that I should look for and can check visually, please let me know.

[BPMSport]

Originally Posted by donsrno1

1. Is it safe enough to drive the car like this, or are there any significant risks of damage etc. from driving? or does the engine drop to limp mode before any serious damage could be done?
I called my service advisor at BMW who said just to drive it till I could bring it in (this would be minimum 400 miles - I'm currently away from home with no BMW dealerships, or garages I would want to use within 100+ miles). However, I'm not entirely sure I trust his judgement from previous experience and want a second opinion. He essentially said if it was serious enough that I shouldn't drive, it would turn the SES light red and start flashing at me..

Your service advisor is clueless. The SES light will never turn red (it can't), and it wouldn't flash unless there was severe detonation for a prolonged period of time.

I don't think you'll induce any damage by driving 400 miles, if you drive casually. The only time you really should avoid driving the car at all, is if it's in "limp-mode", which will show Engine Malfunction on the iDrive, etc..

Originally Posted by donsrno1

2. What are the likely outcomes, and are there any checks I can do myself before driving much or taking to dealership/garage?
(I've read process is basically to check for exhaust/vacuum leaks, then check o2 sensor after cat, and if it seems ok replace the pre-cat o2 sensor). However, is there any of that I can do without any major tools, or by buying any fairly cheap items? (I'll check for leaks, but more interested in checking o2 sensors as I've never done it before)

Car probably needs a low pressure fuel sensor, or an oxygen sensor. I would venture to say that it's the bank one pre-cat oxygen sensor causing the problem.

Originally Posted by donsrno1

3. The dealership recently removed my DCT transmission to fix a leak, then reinstalled it (all under warranty). Is there anything in this process that could have lead to the issue?

Anything is possible. If they hit/banged the sensor during exhaust removal, that could cause something like this. Likely more of a coincidence.

Good luck with the repair, and don't worry about driving it.

[dparm]

Agree with Mike. Limp-home mode will give you shitty gas mileage but it's fine for temporary driving (i.e. getting it to the dealership within the next few days). Just keep the engine load low.

If you have basic tools and time to wrench at home, get under the car and inspect + clean the O2 sensors. You can clean them with electronics cleaner, which can also be used on the harnesses. Inspect for any obvious damage like a broken wire, loose clip, cross-threading, black spots/leaks, etc.

[donsrno1]

Thanks for the advice all.

dparm - I'll look into doing this later.

Otherwise, any experience from others who have had this code appreciated, and I'll update on the caused once I get it all fixed.

[donsrno1]

One more question on this - I occasionally hear a noise as though fluid is dripping on something hot as soon as I turn off the engine (I assume something dripping on the exhaust?).

The noise goes on typically for a minute or so after switching off when it occurs, with 1 'drip' noise every 10 seconds or so. Is this normal/a known thing to happen, or could it be linked to my issues? I'm going to try and investigate the source of noise later. There is no indication of a leak under the car, other than the normal A/C condensate, and I've never heard the noise with the engine running.

[BPMSport]

Originally Posted by donsrno1

One more question on this - I occasionally hear a noise as though fluid is dripping on something hot as soon as I turn off the engine (I assume something dripping on the exhaust?).

The noise goes on typically for a minute or so after switching off when it occurs, with 1 'drip' noise every 10 seconds or so. Is this normal/a known thing to happen, or could it be linked to my issues? I'm going to try and investigate the source of noise later. There is no indication of a leak under the car, other than the normal A/C condensate, and I've never heard the noise with the engine running.

Normal.

[pbonsalb]

I do not think P2096 triggers limp home mode. Just a SES. Limp home mode is rpm limited to 4250 though it seems to kick in at more like 3500, and you won't be able to accelerate very hard or go over 85 mph. Maybe there are variations of limp home mode.

I have P2096 and no driveability issues. I have been playing around with a BMS DP Fix for the x-pipe to dial it in after loading 240E software (no issues with 100E software and previous BMS DP Fix setting).

[BPMSport]

Originally Posted by pbonsalb

I do not think P2096 triggers limp home mode. Just a SES. Limp home mode is rpm limited to 4250 though it seems to kick in at more like 3500, and you won't be able to accelerate very hard or go over 85 mph. Maybe there are variations of limp home mode.

I have P2096 and no driveability issues. I have been playing around with a BMS DP Fix for the x-pipe to dial it in after loading 240E software (no issues with 100E software and previous BMS DP Fix setting).

Limp mode RPM limits vary depending which emergency program it is...

It's not always at 4xxx rpm. It depends if the fault was triggered in E1, E2, or E3 control - these are levels of management internal to the DME.

This particular fault will not cause limp mode. Limp mode will always have a corresponding emergency program fault.

[donsrno1]

Another question, incase these items are linked:

Recently, I've noticed that if I start the car a few hours after it was last run (~1-8 hours say), it goes through the 'Cold Start' cycle, but at the point where the car normally quietens down (~0.5-1 minutes after start up), it doesn't fully quieten down, but actually still sounds a little like it's still in the cold start cycle. When this happens, if I turn off and start the car again it goes through what I would consider a 'normal' cold start cycle (elevated noise for ~30 secs, then reduces to a normal quiet idle). Could this be linked to the error code I got, as I believe the cold start cycle is related to warming up the Cat and hence could be emissions related?

[BPMSport]

Originally Posted by donsrno1

Another question, incase these items are linked:

Recently, I've noticed that if I start the car a few hours after it was last run (~1-8 hours say), it goes through the 'Cold Start' cycle, but at the point where the car normally quietens down (~0.5-1 minutes after start up), it doesn't fully quieten down, but actually still sounds a little like it's still in the cold start cycle. When this happens, if I turn off and start the car again it goes through what I would consider a 'normal' cold start cycle (elevated noise for ~30 secs, then reduces to a normal quiet idle). Could this be linked to the error code I got, as I believe the cold start cycle is related to warming up the Cat and hence could be emissions related?

Normal behavior.

[donsrno1]

You're like an M3 encyclopedia for me here Mike! Thanks for your help.

[335m]

Can you update with the resolution of this issue?