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2012 c250, m271 engine. Originally had a p0068 code for map/maf throttle correlation,changed the throttle body,changed the map sensor (to my understanding is the map by the throttle body pictured below) after changing it last night, p0068 disappears and now i have a p0234 and p0236 code. So Im not sure if the sensor i replaced last night was the correct map, If the map i just bought may be bad,or now it's just moved to the map up top because again,to my understanding on this engine,the map on the top, pictured right up top, is the "boost" sensor. So does this mean I had a bad map but my boost pressure sensor is ALSO bad? Any help would be appreciated as this problem has been plaguing me for over a month now. Also as a note, I have checked for leaks in the possible places. Don’t see any cracked hoses or anything. I have put the original map back on as with the new one it went into limp mode with those boost codes so i’m back to being stuck with P0068
Can you pls provide fault code description along with the issues you need help with ?
Chronologically ordered begining to end:
When did this start?
What happens?
What does testing shows?
what repairs were involved?
What engine type/mileage?
Yeah,
-Had this problem since I got the car a month ago
-Nothing really, car runs and drives fine like it has boost, the CEL is just illuminated for the p0068 (Map/Maf throttle correlation) if i run the original map sensor, if i try running the new one i got from autozone i get p0234 and p0236 (Turbo/Super Charger Overboost Condition) and (Turbo/Super Charger Boost Sensor A Circuit Range/Performance) and when i run it with that map the car goes limp mode and has no power,barely drives)
-testing that i’ve down so far outside of replacing parts is just swing rev testing watching my map values,on my scanner both maps seem to be reacting fine to my revs,voltage wise not sure as my scanner won’t show me volt readings
-repairs so far have involved replacing the MAP as i’ve explained and the throttle body with no change in the code.
And get rid of the K&N filters if you still have them. Bad news for sensors.
Im not sure if that was just a sticker the previous owner had put on,because when i opened the intake box it seemed the filter had the orange around it,is that correct? as i thought the K&N filters had a black outline?
-Nothing really, car runs and drives fine like it has boost, the CEL is just illuminated for the p0068 (Map/Maf throttle correlation) if i run the original map sensor, if i try running the new one i got from autozone i get p0234 and p0236 (Turbo/Super Charger Overboost Condition) and (Turbo/Super Charger Boost Sensor A Circuit Range/Performance) and when i run it with that map the car goes limp mode and has no power,barely drives)
-testing that i’ve down so far outside of replacing parts is just swing rev testing watching my map values,on my scanner both maps seem to be reacting fine to my revs,voltage wise not sure as my scanner won’t show me volt readings
-repairs so far have involved replacing the MAP as i’ve explained and the throttle body with no change in the code.
- engine is m271 and i’m at 189,000 miles
There's something mixed up...
You just got a 200kMi M271 with a map fault
Replacing map with new autozone causes limp mode... lets guess: wrong cross-referenced.
Let's use original part, test it then attempt progress:
Read your original MAP with "Key On Engine Off" to confirm old MAP circuit is good/bad.
Troubleshoot your air injection control valve for leak.
Last edited by CaliBenzDriver; Jan 4, 2025 at 10:53 PM.
Im not sure if that was just a sticker the previous owner had put on,because when i opened the intake box it seemed the filter had the orange around it,is that correct? as i thought the K&N filters had a black outline?
The (in)famous K&N filters have black gaskets and red filter medium. The filter medium is red because K&N developed a “high flow” filter with low pressure drop that used a tacky red oil on it to trap particulates. It’s a great idea if: 1) You are interested in gettIng that last 0.01 seconds that might win the NHRA Funny Car title; and 2) You know how to use it. Since neither of those are true, even for me, it’s useless marketing hype. And what’s worse, most buyers resorted to the “more is better” philosophy and hosed down the filters with so much red stuff it gunked up the entire air induction system.
If you have an orange gasket with a tan medium, you’re good as long as it’s fairly new.
I dont see it there... only turbo boost control solenoid.
I am not sure you can have both turbo + exhaust air injection.
Double check... you are after air pressure that should not be in the intake....turbo solenoid is very qualified to mess that up.
Last edited by CaliBenzDriver; Jan 5, 2025 at 02:25 AM.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Originally Posted by windoge
Im not sure if that was just a sticker the previous owner had put on,because when i opened the intake box it seemed the filter had the orange around it,is that correct? as i thought the K&N filters had a black outline?
The filter element is pink on a K&N basically from the red oil used. If it did have a K&N previously, that could have contributed to your MAP error.
Mercedes cars are very temperamental when it comes to electronics. Best to use original Genuine Mercedes parts or those listed as OE (not OEM). https://www.fcpeuro.com/page/oe-academy
Also, keep in mind you won't see significant boost when the transmission is in Neutral or Park. You need to have a load on the engine for the wastegate to close.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Originally Posted by CaliBenzDriver
I am not sure you can have both turbo + exhaust air injection.
You can if we are talking about secondary air injection, which is an emissions control component when starting a cold engine. My Audi TT 1.8T has one. Never looked for one on my SL400.
Hey@windoge , that is your MAF/boost pressure sensor on the intake pipe.
The MAP is the one underneath that that's literally inside the intake manifold.
I had this issue come up over a year ago. You will want to be sure to use genuine OEM/MERCEDES sensors. I purchased them off eBay and one from my local MB dealer.
You did say you replaced your throttle body? There is a gasket inbetween the throttle body and intake manifold, did that get damaged or shift while reinstalling the new throttle body? That will definitely cause a check engine lights/codes. If you lookup on YouTube this issue, "the flexx garage" posted a video about this.
Did you remove your intake manifold to put on the new throttle body? If so, did you replace the intake manifold gaskets ?
A smoke test would be good at this point to check for any leaks you can't see with visual inspection.
Double check your sensors are fully seated in the intake manifold and in the intake pipe.
Keep us updated!
You can if we are talking about secondary air injection, which is an emissions control component when starting a cold engine. My Audi TT 1.8T has one. Never looked for one on my SL400.
M271 has a secondary air injection pump. It’s driven electrically, not by the serpentine belt like an AIR pump. There is a check valve, but since it’s electric it’s probably controlled by various inputs to the ECU and there might not be a control valve as such. I have never had to go deeper, so I’ll stop here.
Hey@windoge , that is your MAF/boost pressure sensor on the intake pipe.
The MAP is the one underneath that that's literally inside the intake manifold.
I had this issue come up over a year ago. You will want to be sure to use genuine OEM/MERCEDES sensors. I purchased them off eBay and one from my local MB dealer.
You did say you replaced your throttle body? There is a gasket inbetween the throttle body and intake manifold, did that get damaged or shift while reinstalling the new throttle body? That will definitely cause a check engine lights/codes. If you lookup on YouTube this issue, "the flexx garage" posted a video about this.
Did you remove your intake manifold to put on the new throttle body? If so, did you replace the intake manifold gaskets ?
A smoke test would be good at this point to check for any leaks you can't see with visual inspection.
Double check your sensors are fully seated in the intake manifold and in the intake pipe.
Keep us updated!
Ant
are you talking about the one directly connected to to the throttle body pipe?
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Originally Posted by Odd Piggy
M271 has a secondary air injection pump. It’s driven electrically, not by the serpentine belt like an AIR pump. There is a check valve, but since it’s electric it’s probably controlled by various inputs to the ECU and there might not be a control valve as such. I have never had to go deeper, so I’ll stop here.
The SAI pump on my Audi is also electrical. It only runs momentarily when the car is started and injects air into the exhaust stream to heat the cat more quickly.
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