Playing around with my scanner I can read the on-board monitoring test for the fuel system bank1 and 2.
Both tests fail.
The stated range is 4.5 to 650% with bank1 at 1.45% and bank2 at 1.82%.

Does anyone know what this is actually measuring?

Any other ideas on my fuel trim issue?

Thanks
Brian

 

Playing around with my scanner I can read the on-board monitoring test for the fuel system bank1 and 2. Both tests fail. The stated range is 4.5 to 650% with bank1 at 1.45% and bank2 at 1.82%. Does anyone know what this is actually measuring? Any other ideas on my fuel trim issue? Thanks Brian

I have the same problem as your having. Replaced MAS, Replaced a few vacuum lines, Fuel Pump was replaced like yours 60k miles ago. Did you ever solve the problem? I have 2007 C230 Sport, my thinking is the intake manifold is worn and causing problem and/or fuel injector? Keep getting P0170 & P0173 Fuel Trim Malfunction?

 

I dont have an answer yet. After all the changes I mentioned above the numbers are just low enough it doesnt trigger the DTC. I have not tried testing or changing the injectors as I have a hard time believing that injectors in both banks are leaking at the same rate. Of course there isnt really much left in the system that could be wrong at this point. I will probably get to testing them eventually but just too many other things in life I need to deal with 1st.

My DTC was a little different then yours, mine was a P2180

Do you have a scanner where you can read the following values, if so what do yours read (at idle)?

MAF value
Long Term Fuel Trim - both banks
on-board monitoring test for the fuel system bank1 and 2

Thanks
Brian

 

Thanks for responding!

Background, 3+ years ago I removed intake manifold because plastic linkage to short/long runners Butterfly link broke (installed aluminum kit). Passed smog.

2 years ago got cam shaft timing sensor errors. Replaced oil/filter (still error), replaced camshaft timing sensors and position sensors errors fixed.

Now P0170 / P0173 Fuel Trim both banks. When I removed repaired intake manifold, I replaced some worn vacuum lines, I also noticed some manifold seals were looking bad and plastic runners were marginal. I decided to install and it passed smog at that time.

Here are some #’s at idle:


Short Term % Fuel Trim bank1 -0.78% to -1.56%
Long Term % Fuel Trim bank1 6.25%

Short Term % Fuel Trim bank2 -0.78% to 0%
Long Term % Fuel Trim bank2 0.78%

Intake Manifold Absolute Pressure 52kPa
Timing Advance 9%
MAF airflow rate 3.16g/sec

Oxygen Sensor 2 Bank 1 Voltage 0.61%
Oxygen Sensor 2 Bank 1 short term fuel trim n/a %
Oxygen Sensor 2 Bank 2 Voltage 0.68%
Oxygen Sensor 2 Bank 2 short term fuel trim n/a %



Oxygen Sensor 1 will de range current (ma) -0.02ma
Oxygen Sensor 1 wide range equivalence ratio 14.71
Oxygen Sensor 5 will de range current (ma) 0.07ma
Oxygen Sensor 5 wide range equivalence ratio 14.66

Fuel input % 64%

I have electronic background and have been a gear head since high school. I’ve heard the fuel trim specs -10% to +10%?

I don’t have anything verified as what the ranges should be for any of these sensors.

Fuel pump replaced by Merz Dealer Approx 65k miles ago.

Any guidance or thoughts appreciated!

 

Ive had similar issues as you, replaced that crappy plastic linkage with the aluminum one about 3 years ago as well.
Honestly your fuel trim numbers are not that bad. They are within the normal range (I believe your +/- 10% is correct), shows bank 1 was running a little lean and it is adding fuel to compensate. But 6% should not be an error from what I understand.
Mine are at around -30% for both banks, way outside the expected normal range.
Your MAF reading is close to, but lower then, mine. From what I have read it should be more like 3.5 so maybe your MAF is reading a bit low? That would cause it to run lean and have to add fuel to compensate but I would expect both banks to run positive together not just one.
I will try and compare the rest of your numbers to what Im have on mine and report back later tonight.
Just like you I have had a hard time getting good expected values for these readings so I am not 100% sure what to expect from them.

I dont quite understand why you are getting a DTC from what you show here, your values all seem reasonable. If you let it run for a bit (idle and under load) do the fuel trims vary wildly? You expect the STFT to move around but the LTFT should be mostly constant. Definitely constant at a steady RPM and load. Your two codes tell us the controller thinks it can not control the fuel/air mix correctly but the values you list here are well within their controllable range.

FWIW, Im not a mechanic, just an electrical engineer that likes to work on my own cars/trucks so I am not an expert in any way...

Brian

 

Thanks Brian,

Sounds like we have similar backgrounds & Merz problems. The MAS was replaced and originally error went away for 120+ miles but reappeared after I shutoff the engine. Now, I can’t make it beyond 20 miles and error reappears.

I think the error must be under load and the range from load to idle might be too great???

I’ll try getting some numbers while driving at speed.

I can only think the manifold seals might have gone bad and/or plastic runners which could cause vacuum leak under load? Just a hypothesis.

Thanks again!

 

Welcome to the forum @mikep6565 - please take a moment to read the information on the link below. It explains how to update your user profile so that your car's details and your location appear on each post below your avatar. This is good information for others to know when trying to help. It also has good information about how the forums are organized and how to use the search feature:

Find your Forum Section, Navigate & Search

 

I just hooked the scanner up again and here are the differences I see from your number to mine (all at idle):
MAF: 4.7 g/s (seems high for idle, maybe this is my whole problem) My last notes showed 3.5 at idle. Maybe someone else without a current problem can let us know what the MAF reads at idle for them.
Timing advance: bounces a bit but around 12%

my fuel/air ratio shows 99.7% of ideal, yours are right around 14.7 as well so for all the other issues the computer is able to get the ratio where its supposed to be (assuming the O2 sensors are working correct)
Keep in mind my LTFT are way negative (-29%) so dont assume all my numbers are good.
Brian

 

I have some warm-up #’s and driving #’s. Since last clear and still no errors. I’ll post later but they were out of the 10% range. Manifold pressure changed as well. I believe around Longterm trim 28% but will post exact #’s later tonight.

I removed air box to clean MAS and noticed oil blown out from the lower Air Mass Meter Plastic elbow that connects to manifold. Ordered new Mass Air Flow Sensor Gasket - Upper & Lower from partsgeek.

I’ll post Pre gasket replace/MAS clean #’s.

I’ll than try new gaskets and clean MAS and record new #’s.

I figure worth a try. I’m also checking other vacuum lines and will report if I find any bad. So far all look good as I replaced worn hoses when I replaced cheap plastic manifold rocker arm.

Mike

 

 

After cleaning the MAS o-rings and installing original MAS, the numbers looked stable didn’t change much from idle to driving. Manifold pressure was much more stable and didn’t change much at all.

 

I drove the car and had no errors for 51 miles, although there was a P0170 code in the buffer it was pending and no DTC.

After coming off freeway onto street speeds 35mph the codes tripped chk eng light P0170 & P0173.

What I noticed most is both banks tracked little better together & manifold pressure didn’t change much under higher RPM after finding the o-ring issue.

Tomorrow new MAS O-rings arrive and will install.

 

Here are post MAS o-ring clean #’s at idle:


Short Term % Fuel Trim bank1 -5.47%
Long Term % Fuel Trim bank1 -3.91%

Short Term % Fuel Trim bank2 -5.47%
Long Term % Fuel Trim bank2 -6.25

Intake Manifold Absolute Pressure 38kPa
Timing Advance 7%
MAF airflow rate 3g/sec

Oxygen Sensor 2 Bank 1 Voltage 0.7V
Oxygen Sensor 2 Bank 1 short term fuel trim n/a %
Oxygen Sensor 2 Bank 2 Voltage 0.68V
Oxygen Sensor 2 Bank 2 short term fuel trim n/a %



Oxygen Sensor 1 wide range current (ma) 0.07ma
Oxygen Sensor 1 wide range equivalence ratio 15.24
Oxygen Sensor 5 wide range current (ma) 0.05ma
Oxygen Sensor 5 wide range equivalence ratio 14.49

Fuel input % 56

 

MAF numbers didnt change much but your LTFT #s are quite a bit different. Be interesting to see where everything is at when you are finished.

Brian

 

Your correct, before it tripped I check buffer and it only showed LTFT pending error.

The numbers in the beginning held lower with little change but after driving a bit started to drift. Manifold was 38kPa held for a while only slightly changing as rpm increased maybe 51kPa but would settle 45 to 50kPa at 2600rpm range while driving. Difficult to catch errors while driving the vehicle and monitor sensors. I could pay for an option on my scanner which would allow me to recorded sensors. Idle most of the time #’s are fine.

If new O-rings and new MAS don’t fix, I’m ordering a new manifold and gaskets if both errors repeat LTFT & RTFT. I need mention my mileage is 191,000miles.

Since both banks fail, it’s got to be a vacuum leak. Manifold fluctuates quite a bit idle 38kPa to 89kPa 2000-2600rpm range, intermittently. Might even go higher but I’m not able to catch it.

I’ve heard the manifold pressure shouldn’t change much, but again I don’t have any factory #’s to go by.

Mike

 

The difference between your P2180 & my P0170 & P0173 is the following fuel pump/regulator, fuel filter, catalytic converter, I assume the exhaust leak is related to the catalytic converter fail.

You’ve replaced both Pre-cat oxygen sensors I assume and MAS. Pre-cat oxygen sensor is related to secondary air feedback and activation. Checked for vacuum leaks/Air Inlet Pipe? I assume this is the air manifold?

If you live in the country/rural near fields etc mice/rats could eat at the MAS wires. I don’t think this is your fault but troubleshooting a faulty wire I would say is last on your list.

If your fuel pump was replaced like mine, I was told both my fuel pump and filter were replaced because it’s a difficult repair removing rear seat so also replace fuel filter at that time (mine was by dealer).

There is a fuel tank fuel pressure sensor which can go bad. Different from my errors.

Fuel injectors, I used Lucas Fuel Injector Cleaner $12 full bottle treats about 10 tanks and should clean the injectors. I did this being $12 cheaper than $100’s for new injectors.

Catalytic converter? I don’t understand the theory behind this error. I’ve heard a rich fuel mixture can damage cats. You, I believe are running rich. A exhaust leak could indicate too much air this resulting in more fuel being dumped via the oxygen sensor?

Also, if fuel pressure is high maybe your running rich?

Here is a list of possible problems for P2180:

What causes the P2180 code?
There are many causes that could create the conditions in which the P2180 code would be stored. Those may include:

• Faulty or contaminated mass air flow sensor
• Faulty or contaminated mass air flow sensor wiring
• Cracked or broken air inlet pipe
• Faulty oxygen sensors
• Faulty fuel pump
• Faulty fuel pressure regulator
• Clogged fuel filter
• Vacuum leak
• Failed catalytic converter
• Exhaust leak
• Fuel injector
• Common Repairs Needed for the P2180 Code
  • Oxygen Sensor Replacement
  • Mass Airflow Sensor Replacement

Your mileage not as high as mine but I’d start at $12 Lucas Fuel Injector Cleaner, Try checking for an exhaust leak, than double check no vacuum leaks including air intake & MAS including o-rings!

Lastly, try post cat sensor if no exhaust leak, and fuel pressure regulator sensor unless it’s expensive.

I used a mirror today to verify MAS was seated correctly. The clip on back of airbox is important as well to get a good seal. These pesky German engineers are precise from my semiconductor experience, I cleaned my K&N air filters and even the thin screens on the air intake manifold under each filter with carb cleaner! My errors are close to passing so I’m trying little things as well hoping they all add up.

Mike

 

With both banks negative with similar values and no other DTCs I dont think its a leaky injector issue but I havent tried to test for that yet. Feels like they would all have to be failing at roughly the same rate to cause this and not have other issues.

Any ideas on other things that could be causing this condition?

Thanks
Brian

NO. Since your O2 sensor is reading a composite of the entire bank, all it takes is one bad injector on a bank to cause fuel trims to go down if it's leaking, or up if it's not spraying enough fuel. The question is, is it likely to have a bad injector on each bank at the exact same time? Remember, negative fuel trims mean the O2 sensor isn't sensing enough oxygen in the exhaust stream on average, especially when the computer is testing toward the lean condition, so the computer keeps cutting back on the fuel spray duration (which is what the trim number represents as negative trim), until the computer gets a reading from the O2 sensor that when the computer sends less fuel to the bank, the O2 sensor has a drop in voltage, indicating some oxygen is then present in the exhaust stream, and based on the voltage generated by the O2 sensor, the computer checks to see if it's in the correct range or not. You should run live data on the O2 sensor(s) and see what the voltage swings are...these swings should happen about 10 times per second and go from about 0.1v - 0.9v (the higher the voltage the less oxygen present in the exhaust stream.)

Vacuum leaks cause positive trim numbers, and I have yet to see an exhaust leak bad enough to cause O2 sensor reading issues, where you couldn't already hear your exhaust leaking. (I've had cracked exhaust manifolds that didn't throw off the O2 sensor.)

Now, how about your manifold tumbler flaps? I would think you should get a code for them not working right/not being in the correct position, but if they were stuck in a certain position, you might have a condition where your air flow is restricted to the point that the computer has to lean-out the engine. And since the flaps on both banks are typically linked together, this would cause the problem on both banks at the same time.

Fuel pressure could do it as well, but 5 psi high doesn't seem to be enough to make a difference.

 

Interesting and thanks for the input. Brian’s code is P2180, mine is P0170 & P0173 Fuel Trims both banks, the numbers oscillate slightly at idle but stay within +/-10% which I was told were in spec. I have 191,000 miles on the car. I did replace the manifold rocker for long/short runners about 3 or 4 years ago.
When I replaced upgraded rocker I replaced many worn vacuum lines. Also, fuel pump & filter were replaced about 60k miles ago. I have now installed a new MAS and MAS gaskets, new air filters as well. My thinking is during load driving the manifold pressure fluctuates too much manifold pressure going as high as 91kPa and fuel trims reaching 28% as speed changes from freeway 65-75 mph to 0-35mph city street. This is where I see mine trip P0170/P0173.

I’m leaning towards the manifold is bad with a leak somewhere for P0170/P0173.

If there is something else let me know.

The P2180 code fixes I found on the internet in multiple sites. It wasn’t as much a sure fix but to stimulate thought and maybe come up with some solution. You seem to understand the fuel trim numbers better. Trying to help Brian and also myself in my DTC’s.

Mike

 

Not a mechanic but my thoughts in order of priority. 1. Problem with MAF sensor or gasket, etc. 2. Leaking injector (s) 3. Clogged CAT. Don't think vacuum leak manifold gaskets would drive LTFT negative in fact quite the opposite. 1st suspect would be injectors if it were on just one bank but as both are negative I suspect MAF. My $0.02.

 

I do use lucas fuel injector cleaner. I also removed all the injectors and made a little setup to pressurize with injector cleaner and pulse with a battery to turn on. ran them all until they looked great and put them back. Of course my pressure wasnt at 60psi but I didnt notice any leaking when running the cleaning cycles. Didnt notice any difference afterwords.
Lou, I agree I dont have to have all 6 injectors failing at the same rate just both banks failing at the same rate. Any combination of leaking injectors would do it. Still, not very likely, thats why taking out and messing with the injectors was the last thing I tried.

I have measured the fuel rail pressure, it stays right at 60psi which I believe is correct.

Any yes, when replacing the fuel pump it replaces the filter as well.

And I did have the tumbler flap issue a few years ago and it does trigger a DTC (dont recall which one) but that is what caused me to remove the intake manifold and replace the broken plastic actuator with an aluminum one. I guess I should get the boroscope out and look over that whole setup again just to make sure nothing is broken.

Im starting to think my MAF reading is too high (even though I replaced it). My notes when this first started showed 3.4 g/s but now I get numbers like 4 to 4.7g/s at idle. Of course I first had the problem when it was running 3.4 at idle... Seems to show lower when warmed up and higher when at idle after just starting the car. If it thinks it has more air then it really does then the map is going to say to add too much fuel for the real amount of air. Causing it to run rich and causing the fuel trims to go negative to compensate. Does anyone know for sure what the MAF should read at idle?

Brian

 

Im starting to think my MAF reading is too high (even though I replaced it). My notes when this first started showed 3.4 g/s but now I get numbers like 4 to 4.7g/s at idle. Of course I first had the problem when it was running 3.4 at idle... Seems to show lower when warmed up and higher when at idle after just starting the car. If it thinks it has more air then it really does then the map is going to say to add too much fuel for the real amount of air. Causing it to run rich and causing the fuel trims to go negative to compensate. Does anyone know for sure what the MAF should read at idle?

Brian

You could try cleaning the MAF, watch this video:
Diagnosing a Faulty Mass Air Flow Sensor: P0171 P0174 Lean Codes
One thing this guy says to check is if you have any MAF reading with the engine not running ?
Also, DON'T buy no-name white-box parts from places like Amazon or eBay... Rockauto.com has a wide variety of parts brands available in almost every category. And even though Rockauto.com has a range of manufacturers for most parts, I've never seen any I would consider garbage...but still, you get what you pay for. I've saved upwards of 45% on the highest priced part over the same brand at the store. They even tell you which of their warehouses a part is located at, so you can buy other parts that are at that warehouse and minimize shipping cost. Put KLAVAN in the "where did you hear about us" box at check-out.

 

I replaced intake manifold today! Broken vacuum rods which I’ll post pics later. Rigged a fuel injector clean using 12V from battery and individually sprayed GUMOUT cleaner through each injector. New lower o-ring installed.

I’m almost done installing new manifold but pretty confident new manifold going fix my P0170 & P0173 DTC!

Replaced all worn vacuum lines with merz spec lines. Guess when I replaced rocker should have just replaced the manifold!

 

What was the result? Did you get it all fixed?

 

Mixed result right after install P2015 & P0106 errors. Double checked elect connectors and vacuum hoses. Found front vacuum hose kinked and touching manifold metal link & plastic rod link to runners. Also found MAP sensor vacuum hose kinked. Also, found I didn’t fully connect an fuel injector which caused a misfire error.

P2015
Status: Confirmed
Possible decryptions (note control module);
OBDII: Intake manifold air control actuator
position sensor/switch, bank 1 - range/
performance problem

P0106
Status: Confirmed
Possible decryptions (note control module);
OBDII: Manifold absolute pressure (MAP) sensor/
barometric pressure (BARO) sensor - range/
performance problem

Cleared DTC’s and no errors. Car idles MUCH better! Accelerates smoother and quicker. Overall running much better.

Disclaimer, manifold definitely bad as you can see from photos. But a car like mine with 192,000 miles I believe is fighting multiple problems at least 2.

1. Manifold
2.

More comment below!

In my driveway I started the Mercedes Drive Cycle check list to pass each set point Cold Start, EGR, Catalyst etc (I’ll post this because it helps diagnoses). I drove freeway and city streets with lots of stops and accelerations. I had the P2015 code pop-up in the buffer as pending - I was thinking maybe the manifold actuator flaps need to be broken in. Took to some straight away farm roads and opened the car up, romped on it. No error codes and was running like new. Drove the car home with about 60 miles on it. The P2015 code was confirmed but doesn’t trip Chk Eng Light so it still should pass smog. All tests except Cold Start passed - because according to Mercedes you need two consecutive Cold Starts to pass.

Next morning again pass Cold Start etc. So, around 95 total miles I was going through Mercedes Drive Cycle to pass catalysts test, my fuel bank errors P0170 & P0173 came up in the buffer as pending! But they never tripped the Chk Eng Light! Took car home with 121 total miles. Turned car off and codes are gone! Only code is P2015 which doesn’t trip ChkEng Light.

So…I had to hang up trouble shooting more since I had a planned vacation. When I get back I’ll pick it back up.

This was taken during my Cold Start process holding at 1400rpm range for 7 min compared to where I ended.

Not sure if smog will pass with Status Since DTC reset or if I have to have the Current Drive Cycle Status pass all tests I order to pass smog?


Here were my last results:

 

Not sure what to do next on my 192,000 mile C230 but I’m not giving up. Any insight let me know 👍

Hope this helps! Mike

Here is the Mercedes Drive Cycle:

 

Sorry above is out of order but read last 1st than arranging 1 thru 7.

Let me know how your troubleshooting is going.

Mike

 

Passed smog!

Even with code P2015 confirmed but no check eng light it passed. Fuel trim errors went away.

I’m going to replace fuel injectors, depending on outcome I’ll try O2 sensors and last maybe MAP sensor.

I’ve neglected maintenance on my C230. Although it passed smog and running better, I still want to improve the idle and overall drivability of the vehicle.

I’m not putting factory parts too expensive and this is just a 2nd vehicle. I’m buying OEM parts off eBay and will update results.

Manifold was main problem!

 

Brian,

I found my final problem which was another vacuum leak. I used a Cole/Palmer digital vacuum/pressure gauge to snoop around. Kept following vacuum lines and found leak as I wiggled line going to my MAP sensor. Although it was intermittent and I passed smog it got worse. #1 I had big vacuum leak at intake manifold and plastic actuators were snapped. #2 was the MAP sensor vacuum line wiggled it and the leak would happen.

I’ve changed out all the vacuum lines, even ordered one that goes to the vacuum pump. Idle and acceleration smooth!

I tried carb cleaner to snoop for the leak but couldn’t find it. Was about to buy a smoke leak checker but found my digital meter and it worked. You might consider a smoke leak checker.

I’ve now started long over due maintenance to oil recirculation & camshaft plugs. Will do a transmission flush & filter, differential oil.

Overall, my 2007 C230 Sport running strong again. At 193k miles I’m amazed how it’s running. Hoping to go past 250k miles!

Goodluck!