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Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4269
Experience:  15 years master certified 100% fix rate and have access to factory radio codes, wiring, and instructions.
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I'M having a problem diagnosing a 150300 code on a 09 ml320

Customer Question

I'M having a problem diagnosing a 150300 code on a 09 ml320 bluetek i can't find any real definition of this code the code can't be erased its a current code
JA: Thanks. Can you give me any more details about your issue?
Customer: runs like a top no problems but the code turns the ck eng light on after 2 ign cycles without starting the eng. on a cheep generic scanner i get a p0101
JA: OK got it. Last thing — Mercedes Mechanics generally expect a deposit of about $18 to help with your type of question (you only pay if satisfied). Now I'm going to take you to a page to place a secure deposit with JustAnswer. Don't worry, this chat is saved. After that, we will finish helping you.
Submitted: 1 year ago.
Category: Mercedes
Expert:  Lou P. master tech replied 1 year ago.

Hello, i am checking the database for the code, i will need your vin please to make sure i have the correct engine and engine control software. please and thank you

Customer: replied 1 year ago.
the vin is 4jgbb25ex9a499279
Expert:  Lou P. master tech replied 1 year ago.

ok thank you give me a few to check . ill be back

Expert:  Lou P. master tech replied 1 year ago.

you sure its not 105300??

Customer: replied 1 year ago.
no it's a 150300 upper limit HFM-SFI has been exceeded (according to alldata)
Expert:  Lou P. master tech replied 1 year ago.

yes you are correct , sorry the benz info was a little backwards, so the issue is with the right mass air flow sensor, youhave 2 sensors, in the intake in the center of the engine, they clip into the Y pipe that goes to the turbo. you need to replace the right side (passenger side) mass air flow sensor or make sure there is no air leaks in the intake. hope this helps. Lou

Expert:  Lou P. master tech replied 1 year ago.

make sure the car does not have K&N air filters. then swap the air sensors from left to right and see if the codes change or the code adds the other side. that is the easiest test.

Customer: replied 1 year ago.
mass airflow was changed . the engine does not have to run to have the light come on. the code never gets cleared its there as a pending code after its cleared. turn the key off then turn it on the code becomes a hard code
Expert:  Lou P. master tech replied 1 year ago.

what scanner are you using? does it show values like live data?

Expert:  Lou P. master tech replied 1 year ago.

the test in the benz system is to compare data from side to side, if you already replaced the mass sensor then i am curious about the air filters or a leak or you did fix it but the scanner will not erase the codes. you are on the right path.

Customer: replied 1 year ago.
what data would you like the airflow w/eng off is 0 at idle its around 400-500 (don't remember the actual but its in specs)
when opening egr w/scanner its 275. w/ autel maxsys another m/b shop ck it w/autolink
Expert:  Lou P. master tech replied 1 year ago.

both sensors or one sensor? 400-500 seems high at idle. you never answered what kind of air filters are installed? are they new? old? performance?

Expert:  Lou P. master tech replied 1 year ago.

you will need a factory scan tool. mb star diag. the issue is that the system is too lean on the passenger bank and the system cant add more fuel, so the air volume is too much. if you replaced the sensor then the issue is either the code cannot be erased or there is a air leak. or the air filter is a performance air filter and these engines will not operate correctly with any air filter other than the oem dealer filter. you are on the right path but missing something. those are the possibilities . hope this helps . Lou

Customer: replied 1 year ago.
100% stock bluetek 3.0 ihad this apart 6 mts ago to change the oil cooler seals & spent 3 days cleaning the intake manifolds,& ports. the smoke test showed no leaks AND If it was a flow or leak issue the system would not know it when the engine is not running. Im going to connect the air flow sensors bacwards to see if it is the right sensor. whats the code for the left sensor?
Expert:  Lou P. master tech replied 1 year ago.

the possibilites are fuzzy but it looks like

p010b

150100

150200

Customer: replied 1 year ago.
there are many codes for the air flow sensors. but non of these are appearing. I really need to find out what code 150300 means so that i can apply the proper diagnosis strategy,
Expert:  Lou P. master tech replied 1 year ago.

the code means the self adaptation for the right bank has reached its upper limit, meaning the air flow is too great . i can go any further in the test because the sds needs to be hooked up. you need to see the freeze frame data to tell you the difference between the left and right banks and see what it takes to influence the number.

Expert:  Lou P. master tech replied 1 year ago.

the test stops at "compare the left and right mass air flow readings"

Expert:  Lou P. master tech replied 1 year ago.

the code does not point to a electrical issue, so im not sure why your scanner cannot erase the code and it goes right back to pending, you may need to reset the adaptations so the fuel trims start off at 0. does this make sense? i am trying to help here.

Customer: replied 1 year ago.
no it doesn't make sense the lambda adp reading is 0. both af sensors scope to the same readings . i can run the truck with either the right or left a/f individually and get the same readings. i dont think the 150300 has anything to do with the a/f sensors
Expert:  Lou P. master tech replied 1 year ago.

ok, well i can tell you one more bit of info. this may help BUT is confusing. so your fault code did not show up in the list of fault codes under your year and model, but it did for a later engine control module version. i think you need to have the mercedes star diag scan the computer. because that code you gave me is for the mass air sensors.

Customer: replied 1 year ago.
the problem w 150300 has absolutly nothing to do with the air flow sensors. the problem is in the boost pressure circuit.
Expert:  Lou P. master tech replied 1 year ago.

ok, did you get it fixed?

also i can prove to you where i got my info from but it wont matter at this point.

so dont think i made up something, it came straight from the mercedes code database but the issue again was the code was not displayed for your year i had to go a year back.