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2009 S63 AMG P0171 CEL

 
Old 01-23-2017, 10:57 PM
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2009 S63 AMG
2009 S63 AMG P0171 CEL

Forum Members,

I need help figuring out a P0171 CEL on my pride and joy - W221 44K miles

P0171 - System Too Lean Bank 1

Research suggests there are multiple possible sources of the error, including:

- Intake air leaks
- Faulty Mass Air Flow (MAF) sensor
- Faulty front heated oxygen sensor
- Ignition misfiring
- Faulty fuel injectors
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Incorrect Positive Crankcase Ventilation (PCV) hose connection

My reluctance to take the car to a mechanic was that they'd likely just throw parts at it and wait for the CEL to go out. I can do that - I want to do something more logical.

Symptoms: From a cold start the car will fire up normally (at a slightly higher RPM). About 1-2 second after firing/running the revs will collapse but then catch and run smoothly until the idle settles to standard RPM.

If I drive the car for 20-30 mins (or longer) then come to a stop (traffic light, stop sign etc) it will often stall. It doesn't happen all the time, but it seems the longer I've driven it, the more likely it is to do it.

If I've driven the car long enough that its fully warmed-up and has reached the stalling phase - and actually does stall, or if I turn it off, it won't start again while hot without giving it a good bit of throttle. If I try to start it while hot with no throttle it will fire up but then immediately stalls.

Progress so far:

Removed the MAF sensor from bank 1, cleaned with MAF sensor cleaner and replaced. No change. Switched the MAF sensors (from one bank to the other), drove ~160 miles and checked w code reader again, still reporting bank 1 fault. Concluded it's likely not the MAF sensor.

I Bought a iCarsoft MB II- MB Smart Scanner i980-II (New version) and scrolled through the diagnostics and found three errors (see attached PDF for pics):

Note: Engine was warm and idling steadily for ~10 mins before these pics were taken

- EVAP Monitor 0.040" - Fail
- Fuel System Bank 1 - Fail (under lower limit)
- Fuel System Bank 2 - Fail (above upper limit)

Lastly, I would add that while I've never run the fuel tank dry (as in run out), I had run the tank REALLY low 4 or 5 times in the couple of months before the CEL first appeared.

Any thoughts or experience with such issues would be much appreciated.

Simon
Attached Files
File Type: pdf
Screen Shots 4.pdf (4.24 MB, 245 views)
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Old 01-23-2017, 11:28 PM
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I don't have that car, and haven't researched this condition... from your description I would have thought MAF, but you seem to have ruled that out. My next two would be (1) fuel filter (insufficient fuel, but on one bank only?); (2) fuel pump (too expensive a guess); (3) spark plugs (perhaps a previous stab at this with improper plugs); or (4) coil packs (same logic as 3).

If it was my car, I'd tackle (1), (3) and (4), in that order -- all cheap and good to do in any event. If not that, then I'd suspect either the fuel pump or the ECU, both expensive fixes. By the way, how's your battery? Benz SClasses are notorious battery hogs -- faulty batteries don't adequately power the computers, leading to all sorts of crazy faults that make no sense. But the fact that it's heat dependent might say spark plugs.

Hope this helps. Good luck.

maw
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Old 01-24-2017, 01:06 AM
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change your intake manifold gaskets they have been updated to the sls ones
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Old 01-24-2017, 01:38 AM
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Very common for the crankcase vent valve on the back of the intake manifold to leak as well as the intake manifold gaskets leak or the bolts loosen up. Sometimes the purge valve sticks open as well.
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Old 01-24-2017, 12:38 PM
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Originally Posted by benz_addict View Post
change your intake manifold gaskets they have been updated to the sls ones
I seem to have read many times that the intake manifold gaskets and bolts are a weak link in the M156.

When you say they have been updated to SLS ones - should I look to purchase ones that are spec'd for the SLS specifically - and rule out any chance of being given the same flawed variety in the S63?

Thanks for you help.
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Old 01-24-2017, 12:44 PM
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Question

Originally Posted by Rocman8 View Post
Very common for the crankcase vent valve on the back of the intake manifold to leak as well as the intake manifold gaskets leak or the bolts loosen up. Sometimes the purge valve sticks open as well.
Wouldn't a crankcase vent valve leak or sticking purge valve cause both cylinders to run lean? Mine is consistently putting out only bank 1 codes. Just a thought.

I seem to have read that many people have complained about the intake manifold bolts on the M156. Are there replacement (steel or titanium) aftermarket units anyone can point me in the right direction to? Or is it just a better idea to remove them, add some Loctite and torque them down to spec again?

The one thing that I can't understand is why the car is more prone to stalling when hot than when cold. If it is the manifold gasket/bolts, perhaps its due to metal expansion - causing a greater gap and letting more un-metered air in?

Really appreciate the feedback.
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Old 01-24-2017, 12:56 PM
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Originally Posted by sbainb View Post
Wouldn't a crankcase vent valve leak or sticking purge valve cause both cylinders to run lean? Mine is consistently putting out only bank 1 codes. Just a thought.

I seem to have read that many people have complained about the intake manifold bolts on the M156. Are there replacement (steel or titanium) aftermarket units anyone can point me in the right direction to? Or is it just a better idea to remove them, add some Loctite and torque them down to spec again?

The one thing that I can't understand is why the car is more prone to stalling when hot than when cold. If it is the manifold gasket/bolts, perhaps its due to metal expansion - causing a greater gap and letting more un-metered air in?

Really appreciate the feedback.
Your right both banks will run lean however I've seen them many times where one bank is out over specs and the other bank if you look at adaptations is right on the border of the specs so if it's a smaller leak caught early enough then one bank will throw the code first. Just purchase the gaskets speced for the car they will be updated already and you have to replace the bolts as well. They are one time use aluminum bolts no loctite at all and the torque spec was also updated to add an additional thrird step of an additional 10 degrees after the 90 degrees. When the intake is off replace the vent valve in the back they always leak around 50k
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Old 01-24-2017, 12:59 PM
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Do you have some kind of a scanner that you can compare the left and right banks self adaptation values?
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Old 01-24-2017, 01:02 PM
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Originally Posted by Rocman8 View Post
Do you have some kind of a scanner that you can compare the left and right banks self adaptation values?
Yes, I bought the "iCarsoft MB II- Mercedes-Benz/Sprinter/Smart Scanner i980-II New version".

Amazon link:

https://smile.amazon.com/iCarsoft-Me...%2FSprinter%2F
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Old 01-24-2017, 01:34 PM
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Ok let's see the left and right side adaptation values
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Old 01-24-2017, 02:02 PM
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Originally Posted by Rocman8 View Post
Ok let's see the left and right side adaptation values
Rocman,

I actually posted pics with my initial question showing the screen shots from the tool - are these what you're referring to when you say 'adaptation values'?

Thanks again,

Simon
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Old 01-24-2017, 02:12 PM
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Oh I missed those screen shots. Yeah I've never seen values like that before. It's an interesting way the scanner is displaying the information. The minimum / maximum values in the star computer is +- 5% so I don't understand the 650.86% thing that's just weird. Anyways it still looks like both banks failed and just haven't set the other code yet.
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Old 01-24-2017, 03:09 PM
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Originally Posted by Rocman8 View Post
Oh I missed those screen shots. Yeah I've never seen values like that before. It's an interesting way the scanner is displaying the information. The minimum / maximum values in the star computer is +- 5% so I don't understand the 650.86% thing that's just weird. Anyways it still looks like both banks failed and just haven't set the other code yet.
It could be very possible that there is additional functionality with the tool. I just got it and haven't had much time in the evenings to play around with it. I'll play w it some more tonight and see if I can figure out what else it does.

Best

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Old 01-25-2017, 01:34 PM
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Exclamation The Plot Thickens



Originally Posted by Rocman8 View Post
Oh I missed those screen shots. Yeah I've never seen values like that before. It's an interesting way the scanner is displaying the information. The minimum / maximum values in the star computer is +- 5% so I don't understand the 650.86% thing that's just weird. Anyways it still looks like both banks failed and just haven't set the other code yet.
Update (after learning how to use the MB scan tool):

I'm now pulling four DTC (Diagnostic Trouble Codes) after last night's scan (was pulling just one previously):

#1. P0171 (original/current code I pulled a while back) - System too lean Bank 1

#2. P010B (New/current) - Mass or Volume Air Flow B Circuit Range / Performance

#3. P0101 (New/current) - Mass or Volume Air Flow A Circuit Range / Performance

#4. P010B (New/Pending) - Mass or Volume Air Flow B Circuit Range / Performance

#2 and #4 are the same, it's just that #2 is current and #4 is pending.

I did a little further research on the P0101 codes and found this:

"Basically this P0101 diagnostic trouble code (DTC) means that there is a problem with the Mass Air Flow (MAF) sensor or circuit. The PCM detects that the actual MAF sensor frequency signal is not within a predetermined expected range of the calculated MAF value."

Next, I went to the freeze frame data to see the conditions that logged the DTC (expected to find at least 3 but either the car doesn't store freeze frame data for more than one code at a time, or the MB-II scan tool can't read more than one at a time):

DTC That Caused Required Freeze Frame Data Storage P0171

Fuel System 1 Status: CL (closed loop)
Fuel System 2 Status: CL (closed loop)
Calculated Load Value: 26.7%
Engine Coolant Temp: 90C
STFT B1: - 6.3%
LTFT B1: +3.9%
STFT B2: -5.5%
LTFT B2: +6.3%
Fuel Rail Pressure: 360kPa
Intake Manifold Absolute Pressure: 37.0 kPa
Engine RPM: 624/min (Idle)
Vehicle Speed: 0 km/h
Intake Air Temp: 53C
Air flow Rate from Mass Air Flow Sensor: 6.97 g/s
Absolute Throttle Position: 14.5%
Commanded Secondary Air Status: OFF
Time since Engine Start: 130 sec
Commanded Evap Purge: 0.0%
Fuel Level Input: 65.5%
Barometric Pressure: 102 kPa
Control Module Voltage: 13.95V
Absolute Load Value: 17.6%
Fuel Air Commanded Equiv. Ratio: 0.999
Relative Throttle Position: 1.2%
Ambient Air temp. 27C
Absolute Throttle Position ‘B’: 14.1%
Accelerator Pedal Position ‘D’: 6.7%
Accelerator Pedal Position ‘E’: 6.3%
Commanded Throttle Actuator Control: 2.0%



I then pulled the current data stream while idling on the driveway last night (car fully warmed up):


Fuel System 1 Status: CL (closed loop)
Fuel System 2 Status: CL (closed loop)
Calculated Load Value: 36.1%
Engine Coolant Temp: 97C
STFT B1: - +2.3%
LTFT B1: +3.1%
STFT B2: -2.3%
LTFT B2: +9.4%
Fuel Rail Pressure: 360kPa
Intake Manifold Absolute Pressure: 36.0 kPa
Engine RPM: 643/min (Idle)
Vehicle Speed: 0 km/h
Ignition Timing Advance for #1 cylinder: 3.0 degrees
Intake Air Temp: 72C
Air flow Rate from Mass Air Flow Sensor: 4.5 g/s
Absolute Throttle Position: 14.9%
Commanded Secondary Air Status: OFF
Oxygen Sensor Output Voltage (B1-S2): 0.740V
Short Term Fuel Trim (B1-S1) 99.2%
Oxygen Sensor Output Voltage (B2-S2): 0.700V
Short Term Fuel Trim (B2-S2) 99.2%
OBO Requirements: OBD2
Time Since Engine Start: 2450 sec (O2 sensors and cat conv up to temp.)
Distance travelled since MIL activated: 4121 km (terrible I know)
Commanded Evaporative Purge: 23.9%
Fuel Level Input: 92.5%
Number of Warm-ups since DTCs cleared: 255
Distance Travelled since DTCs cleared: 65,535 km
Evap System Vapor Pressure: -273.5 Pa
Barometric Pressure: 99 kPa
Equivalent Ratio (lambda) B1-S1: 0.992
Oxygen Sensor Current (B1-S1): -0.00 mA
Equivalent Ratio (lambda) B2-S1: 0.985
Oxygen Sensor Current (B2-S1): -0.06 mA
Catalyst Temp. Bank B1-S1: 489C
Catalyst Temp. Bank B2-S1: 486C
Control Module Voltage: 14.04V
Absolute Load Value: 22.0%
Fuel Air Commanded Equiv. Ratio: 0.999
Relative Throttle Position: 1.2%
Ambient Air temp. 83C
Absolute Throttle Position ‘B’: 14.5%
Accelerator Pedal Position ‘D’: 6.7%
Accelerator Pedal Position ‘E’: 6.3%
Commanded Throttle Actuator Control: 2.0%

Note: Ambient Air temp is 83 C (not likely) and is greater than air intake temp 72 C. This seems erroneous but even if it is, it didn’t throw out a new code (P0070, 0071 or 0072)



Then I pulled the data stream again this morning (while idling – engine just started):


Fuel System 1 Status: CL (closed loop)
Fuel System 2 Status: CL (closed loop)
Calculated Load Value: 34.5%
Engine Coolant Temp: 61C
STFT B1: - -0.8%
LTFT B1: +3.1%
STFT B2: +0.8%
LTFT B2: +9.4%
Fuel Rail Pressure: 354kPa
Intake Manifold Absolute Pressure: 36.0 kPa
Engine RPM: 653/min (Idle)
Vehicle Speed: 0 km/h
Ignition Timing Advance for #1 cylinder: 3.5 degrees
Intake Air Temp: 34C
Air flow Rate from Mass Air Flow Sensor: 5.0 g/s
Absolute Throttle Position: 14.9%
Commanded Secondary Air Status: OFF
Oxygen Sensor Output Voltage (B1-S2): 0.720V
Short Term Fuel Trim (B1-S1) 99.2%
Oxygen Sensor Output Voltage (B2-S2): 0.725V
Short Term Fuel Trim (B2-S2) 99.2%
OBO Requirements: OBD2
Time Since Engine Start: 308sec (O2 sensors and cat conv NOT up to temp.)
Distance travelled since MIL activated: 4121 km (terrible I know)
Evap System Vapor Pressure: -310.0 Pa
Fuel Level Input: 87.8%
Number of Warm-ups since DTCs cleared: 255
Distance Travelled since DTCs cleared: 65,535 km
Evap System Vapor Pressure: -381.0 Pa
Barometric Pressure: 100 kPa
Equivalent Ratio (lambda) B1-S1: 0.984
Oxygen Sensor Current (B1-S1): -0.06 mA
Equivalent Ratio (lambda) B2-S1: 0.993
Oxygen Sensor Current (B2-S1): -0.03 mA
Catalyst Temp. Bank B1-S1: 429C
Catalyst Temp. Bank B2-S1: 428C
Control Module Voltage: 13.95V
Absolute Load Value: 22.0%
Fuel Air Commanded Equiv. Ratio: 0.999
Relative Throttle Position: 1.2%
Ambient Air temp. 32C
Absolute Throttle Position ‘B’: 14.5%
Accelerator Pedal Position ‘D’: 6.7%
Accelerator Pedal Position ‘E’: 6.3%
Commanded Throttle Actuator Control: 2.0%

Since the STFT specs for both banks (last night and this morning) are fine (less than +/- 5%) everything seems to lean towards MAF sensors. There clearly isn't a vacuum leak at idle or I'd be consistently seeing high (positive) STFT and a far higher sustained (positive) LTFT on at least one of the banks.

Here is what I think is going on. After reading more about these issues this morning I saw commentary about problems people have had when changing out the standard filters for K&N free flow filters etc. I did that, about 10K miles before throwing the first DTC (P0171). I think these filters are the ones that are driving the MAF sensor data crazy (and instigating the codes) as the ECU in-turn can't match the inputs (flowrate and air temp) to the original MAP.

I also think I may have a bad Purge valve. The solenoid should see to it that the PV only opens when commanded but there are a couple of strange things going on. Firstly, when I first started the scanning system it recorded two EVAP system readiness failures: "EVAP Monitor 0.04" and "Purge Flow Monitor".

After I logged all the data above I reset the codes so I could observe a virgin STFT trend (without the compensating LTFT history). What I noticed was interesting. The car would idle without any issues (I was watching the STFT B1 and B2 trends the whole time) and every 10-15 seconds I would observe a sharp spike (up to 15-20%) on BOTH STFT trends, followed instantly with the car attempting to stall. It would recover (barely) without my needing to touch the throttle and would then run smoothly for another 10-15 seconds before repeating the process.

I think the purge valve is opening non-commanded, creating an immediate vacuum which in turn causes the ECU to spike the STFT richer to compensate and identifies the event as a lean condition and blames the whole thing on the MAF sensors. The stalling effect I have been experiencing (and difficulty in restarting) would support this theory as the injectors wouldn’t been dumping a rich dose of fuel to compensate just as it stalled and the now open purge valve is allowing a hydrocarbon-rich vapor into the inlet manifold making things even worse. The only way to restart is to open the throttle and let the car take a huge gulp of air to balance out the burn ratio.
Still not sure exactly why I’ve got a ridiculously high ambient air temp reading or why I’m also failing a fuel monitoring readiness test (in addition to the purge and EVAP ones) – but two things at a time!

I’m going to go and watch the live data of the “Commanded EVAP Purge” as it idles (and presumably stumbles to stay running every 1-15 secs to see if I see any spikes in the sensor output. But first things first, yank the K&N’s and put the original style filters back in.

Anyone think I’m making an ounce of sense here LOL?
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Old 01-28-2017, 02:14 PM
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Issue Resolved

Issue resolved!



I'm posting this as I hope it'll serve as a useful reference to anyone experiencing similar issues, now or in the future. Thank you to Maw1124, Benz Addict, and Rocman8 for their knowledge and assistance. Nice to see that there are still folks out there willing to help others without any expectation of compensation. Props people!

After additional research I found several threads from folks discussing lean code issues after replacing the stock air filters with aftermarket ones. I had missed this discussion completely. I had changed out my filters days after acquiring the car but the CEL didn't come on until ~5 months later. Needless to say, I didn't connect the issues.

I bought OEM filters and pulled the K&N units (charcoal filters still in place BTW). I reset the codes and went for a test drive (approx. 25 miles) while running a live data feed on my scan tool to show Short Term Fuel Trim Bank 1 (STFT B1), Long Term Fuel Trim Bank 1 (LTFT B1), Short Term Fuel Trim Bank 2 (STFT B2), and Long Term Fuel Trim Bank 2 (LTFT B2). I would like to have watched MAF sensor output also but my scanner will 'only' graph four parameters at a time.

I could tell pretty quickly that the car was still driving poorly – correlated with significant positive peaks in both banks’ STFT levels as the ECU continuously attempted to richen the mixture to offset the system leanness. About 18 miles into the ‘test drive’ the check engine light (CEL) returned. The car was still stalling intermittently at idle, had a non-crisp throttle response (not immediately evident to all, but when you know your car…..) and was just not happy. W. T. *. ?!

I got home and ran the scan tool again from the beginning and it bounced back two (current) codes, which were two of the newer codes I’d seen earlier:

P0101 - Mass or Volume Air Flow A Circuit Range / Performance

P010B - Mass or Volume Air Flow B Circuit Range / Performance

Interestingly, the initial code I’d seen (P0171) hadn’t appeared – not even as a ‘pending’ code. Progress of a kind. LTFT B1 had risen to +2.1% and LTFT B2 to +3.9%. This confirmed the lean code I’d originally observed, but the leaner bank was bank 2, not bank 1 - which pushed the original code at the beginning of all this nonsense. Regroup.

So now the ECU is telling me definitively it’s not happy with the Mass Air Flow (MAF) sensors – both of them. Again I reset the codes, pulled the sensors on both banks, and sprayed the CRAP out of them with MAF cleaner before reinstalling. On a side note, I saw the slightest sheen inside both air boxes (presumably from the oil applied to the K&N filters I just removed) so I wiped them out clean before putting everything back together. Took it for another test drive – same route, same everything. Same EVERYTHING. Same crappy response, stalling at idle, and same check engine light back on. LTFTs on both banks continuing to rise (positively), confirming lean running conditions. But still no CEL. I guess I hadn’t quite reached the threshold for the LTFT to max out and trigger the P0171 code.

As unlikely as I thought it was that I’d somehow lost two independent MAF sensors at the same time I resigned to the fact that they need to be replaced, and needed to be replaced quickly. So I began searching for new units online but only seemed to be able to find them as part of a new airbox package. I didn’t need new airboxes – just the sensors themselves. I looked everywhere but couldn’t find any. Weird, but oh well. It was while searching for these sensors that I stumbled across the whole discussion of OEM filters vs. free-flowing, and then charcoals vs. no charcoals, and then standard air boxes vs. ROW (Rest of World) air boxes.

Just when I was about to scream with frustration I noticed a picture that changed everything (see attchment). In a thread discussing a DIY effort to modify the airbox internals someone had taken a pic of their engine bay and asked a question about how to install MAF sensors correctly. Someone had responded to point out that the one on driver's side (in the pic posted) was on upside down. The responder went on to explain that the two MAF sensors (left and right sides) should be installed opposite to each other – and the easiest way to confirm yours are on opposite ways, is to look at the electrical connector. One side should look “smooth” – passenger side bank, and the other “bulky” – drivers side. These are my own descriptions – referring to how the connectors look once they’re snapped onto the sensors.

I went outside to the car to look and I’ll be damned if mine weren’t installed the same manner as in the pic. That is to say, WRONG!! While standing in my garage shaking my head the whole puzzle fell together perfectly. I changed the OEM filters for K&N units in June 2016. The check engine light code P0171 code first came on mid-November 2016 (seemed to be running just fine). I took out both MAF sensors a couple of days later to clean but when I reinstalled them I installed the driver side unit (bank 2) upside down. This is what instigated the second wave of codes relating to MAF sensor issues which I didn’t rescan for until I got my new scanner in Jan 2017. The two sets of codes were unrelated – unless you consider my idiocy as a firm union between the two. Dohhhh!! I removed and rotated the bank 2 MAF sensor 180 degrees, reset the codes (AGAIN), closed my eyes, held my breath and pressed my favorite button in the world.

I’d love to tell you that I knew the second I heard the motor fire that it was fixed, but I didn’t. The reason being is that in erasing the CEL codes you also (at least with my scanner) erase all the learned LTFT specs in the ECU. As such, the car essentially has to relearn and memorize all the finer nuances of how to run and interact all the sub-systems. Anyone who’s a self-admitted nerd will take appreciation from watching the live data stream that shows the internal trial and error that the car is undertaking as it dials-in the perfect conditions for maximum combustion efficiency. After ~10 mins the car was up to temperature and purring beautifully. The STFT B1 and STFT B2 were sitting flat at ~+/- 0.5% so I rolled down all the car windows (its 11pm at night at this stage and I’m still parked in the garage – with door closed, idiotic I know) and I gave the accelerator a foot full.

Holy sh*t. I knew immediately that everything was fixed. The crispness and response of the M156 had returned. I took it for a test drive and it felt like a completely different car. I’ve since driven it 400 miles on an out of state trip and it's running perfectly. No more stalling, no more difficulty starting when hot, no more flat spots. And no more annoying as hell CEL on my otherwise beautiful display. I ran the scanner when I arrived to my destination and there were no codes (current or pending) and all of the OBD2 system readiness logs showed “PASSED” (see earlier post regarding failed tests).
I can’t tell you how glad I am to have my girl back to her old self. Driving on the long two lane bridges between Houston and Louisiana is always fun as there is nowhere for cop cars to hide (the hard shoulders are narrow at BEST). Opening the S63 up to pass others at highway cruising speed is one of life’s little joys LOL and while getting to the bottom of this whole thing has been a saga, to drive the car like this again makes it so worthwhile.

Lessons I learned from this “project” (disclaimer, first time I’d used/owned a scanner, worked on an MB, or ever looked into ECU functions/trends):

1. Document EVERYTHING, and do it methodically. You just can’t take enough pictures. This can be useful not only when you’re putting things back together (a lesson I’ve so clearly learned at this point) but also as a reference/resource to help explain to others EXACTLY what is going on when you’re soliciting help/guidance or trying to assist in a professional diagnosis.

2. Don’t be afraid to erase codes. First off, you’re not erasing them from the car’s ECU so they can’t be displayed again in the future - you’re just erasing them from the stored memory section as they pertain to the specific event or condition(s) that triggered the diagnostic trouble code(s) DTC.

3. When an event is logged in the ECU that generates a DTC and CEL, a ‘Freeze Frame’ of the engine management system is logged. For example, if as in my case the ECU logged P0171 (bank 1 running lean) it also recorded all the engine conditions associated with the error code generation. You can view these conditions with certain scanners to get a fuller picture of what was going on at that precise moment. Utterly invaluable. Also, it doesn’t matter if those conditions remain or even worsen, the Freeze Frame data does NOT update. Meaning, even if the CEL has been on for 6 months and the conditions have gotten worse, the data logged is associated ONLY with the original conditions that first triggered the check engine light. Hence, there’s no issue with erasing the code(s) and letting it/them reappear so you know you’re addressing CURRENT issues. The only potential downside of resetting codes is that there is a nominal period of time/distance necessary before the errors will repopulate. If you need a mechanic to see these codes, reconsider holding off on erasing them right before you head to the shop.

4. Research the symptoms on forums such as this and ask detailed questions. Many of the answers you're looking for can be found without needing to post a thread. Or at a minimum, you can get up to speed with known issues and troubleshoot/eliminate the basis. Many of the MBW forum members have a tremendous amount of knowledge, insight and experience in dealing with MB and AMG related issues. Become engaged, be curtious, and ask intelligent questions

5. Don’t be intimidated by the three-pointed star badge! Roll up your sleeves and take-on projects yourself. MB bolts tighten and loosen just the same way Ford and GMs do. If you don’t try you’ll definitely never know if you could have fixed it yourself, and you’ll never get the satisfaction or feeling of accomplishment when the job’s done and you KNOW it's been done right.

6. Share what you’ve learned. What seems obvious to you after you’ve cracked the code could well be a mystery to so many others. Think how much you’d have appreciated a tutorial of how to resolve your issue before you started. Pay it forward.

Thank you again to all of you who participated in my process of learning and figuring this problem out. I definitely made it hard on myself by installing the MAF sensor incorrectly, but it was a small error that resulted in a lot of knowledge – so a great trade-off in my opinion.

Now I need to figure out if I can somehow get my K&N’s to work without setting off the CEL again for running too lean. If anyone made it this far and has any suggestions – I’m all ears.


Attached Thumbnails 2009 S63 AMG P0171 CEL-both-sides-maf-sensor-place.jpg  
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maw1124 (01-29-2017)
Old 01-29-2017, 09:23 AM
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Lots of good learning here, mostly on the perils of DIY if you ask me. I guess that's why I let trained guys do the work. I like to be educated (via this site and others) just to save them some time and me some money, but they'll be doing the work not me.

Now that your MAF is installed properly, I'll go back to my original statement. You shouldn't have any problem with K&N filters on this car. They don't let in so much air the computers can't adjust.

At the risk of pointing out the obvious, for all you know all the other people reporting these problems after installing K&N filters made the same mistake you did (improper MAF installation).

Although your experience moved me further to going back to factory filters where I have K&N filters. If the goal is clean, cool, compressed air passed by properly reading MAF sensors and into the engine, I'm failing to see how adding oil to "free flow" filters aids that process. Don't get me wrong, I'm not railing against K&N filters. But I think they may have a better home in old Detroit Muscle than in any modern MB AMG (or BMW M) car.

Enjoy!

maw
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Old 01-29-2017, 10:07 AM
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Originally Posted by maw1124 View Post
Lots of good learning here, mostly on the perils of DIY if you ask me. I guess that's why I let trained guys do the work. I like to be educated (via this site and others) just to save them some time and me some money, but they'll be doing the work not me.

Now that your MAF is installed properly, I'll go back to my original statement. You shouldn't have any problem with K&N filters on this car. They don't let in so much air the computers can't adjust.

At the risk of pointing out the obvious, for all you know all the other people reporting these problems after installing K&N filters made the same mistake you did (improper MAF installation).

Although your experience moved me further to going back to factory filters where I have K&N filters. If the goal is clean, cool, compressed air passed by properly reading MAF sensors and into the engine, I'm failing to see how adding oil to "free flow" filters aids that process. Don't get me wrong, I'm not railing against K&N filters. But I think they may have a better home in old Detroit Muscle than in any modern MB AMG (or BMW M) car.

Enjoy!

maw
Maw,

I concur with your reasoning and speculation regarding the 'need' for oil to be added to free flow filters, such as K&N. A friend of mine asked me the same question last week, "why do high-performance air filters need oil and OEM ones don't?" The only thing I can think of is that free(er) flowing air filters are incapable of capturing the smallest entrained particles, and the oil is added to capture such particulates and hold them in suspension - forbidding passage downstream.

In several threads I have read of the perils of over-oiling filters as the excess oil inevitably winds up being drawn through/across the MAF sensors and into the intake components. Not good.

With respect to the issue of why K&N's would activate the CEL 'Too Lean Bank X' - not sure. It seems to be a split camp here on the forum, with many citing issues and many going on without any troubles. My timeline may have been lost in the girth of my posts, but just to clarify, I didn't touch the MAFs until after the first CEL came on - that was what instigated me to clean and replace the sensors.

My plan moving forward is to run a little longer on stock filters so that I can feel really good about this issue being resolved, then switch back to the K&Ns for a few thousand miles. Beyond that I was planning to remove the charcoals, then modify either modify my air boxes or purchase ROWs. On your assessment of the MAFs being able to accurately meter cool clean air, I couldn't agree more. In theory, if more air is getting across them at low revs then such excesses are shifting further into the center of the sensor's operating range.

I will post back with updates on the CEL status (or lack there of) with respect to leanness and the configuration of my filter/charcoals/air boxes. I would eventually like to get the first stage ECU tune from either Weistec or OE, but won't consider this further until I get a reliable and consistent trend of well-metered air flow.

As always, I'd appreciate anyone's input/feedback/concerns etc.... regarding related issues.

Cheers,

Simon
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Old 01-29-2017, 10:13 AM
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Makes sense, Simon. Given your plans, I would skip the K&N filters and go straight to Weistec. It's just one less thing to lose grey matter over. And as you can see, it's easy to lose a lot of grey matter on these Internet boards and complex cars. I trust MB AMG over both K&N and these tuner companies, but that's just me. I can't put down all the power I have, much less use it on the streets, so why risk reliability on more of what I don't need. Conversely, given the cash and grey matter these things consume, I need all I can get.

I have K&Ns on my M3 and on my 500E, both courtesy of the prior owners. But I'm starting to think to go back to stock, at least on the M3.

maw
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Old 07-10-2017, 02:08 PM
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Update. This problem evolved to generating lean codes for bank 1 AND bank two, both 'generally' and while at idle (for a total of four codes).

I finally found the time to remove the intake manifold and swap-out the intake manifold gaskets, bolts, and apply the revised torque specs. I reset the ECU codes and..........bingo! That was 1500 miles ago and not a hint of any CEL. I also removed the injectors to replace the upper and lower seals, and changed out the plugs. The car runs a tad cooler (~5-8 deg. F) and has a sharper throttle response and crispier sound.

Word of warning. I got a little ahead of myself and as I was removing the manifold I got hung-up on the water (engine) temperature sensor lead and sheared the sucker right off. Not the end of the world, $25 for a new one and I was back in the game. Just note, this can ONLY be installed with a 19mm wrench (closed/loop end - not open) due to it's funky position. You can get it with a ratchet and socket, but not before you disassemble the upper portion of the serpentine assembly. No thanks.

I also took this opportunity to replace the PCV (Positive Crankcase Valve) - a doddle when the manifold was out. For the part price of $75 this was a no brainer.
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