IGB

Here is an odd one for you... the important info:

Getting ready to take my 2008 C300 Sport to its first California Smog Check, so out of caution and not to be surprised if something were to come up, I figured I'd do an OBD-II reading to check for any codes.

Sure enough, I get a P0522 which, the closest I can find a description for, goers something like this:

Powertrain: Engine Oil Pressure Sensor/Switch Low Voltage.

By the way, the "Check Engine Light" is NOT on, and yet the code keeps coming up on an OBD-II reader.

Obviously, I checked the oil and the level was a bit on the low side of what is acceptable... I still topped it off and it now sits on the high end of the dip stick marker but still within the acceptable level.

Even after topping off the oil, and clearing the code, it still returned within minutes...

So what gives? Anyone run into this code before on a 2008 C300?

------------------------------------------------------

Mr.Mango

You will need to test the oil pressure sensor voltage output. The BCM sends a input voltage to the sensor, as the pressure changes it creates a different resistance changing the reference voltage returned to the BCM... More than likely its sensor failure. The sensor should have a reference voltage of 5V, most likely your sensor is toast and causing excessive resistance which is causing your low voltage code.

I would also check oil pressure to be safe, there is a test port on the front cover of the engine by the belt tensioner.

Pressures should be as follows...
- 700RPM, 10 PSI or higher
- 2000RPM, 23 - 35 PSI
- 3500RPM, 51 - 68 PSI

IGB

Thank you for you reply and for providing the pressure specs. I actually had those but in “bars” as opposed to "PSIs". It gives me comfort that the conversion has resulted in the same values. Much appreciated.

And thank you for this part as well...

That explanation matches what I have come across for that particular albeit generic OBD-II fault code.

I am not doubting your information, however, there is conflicting information that says: (see post 3 in this thread: Oil sensor in engine which I am quoting below)

This is further semi-confirmed by searching through at Mymercedesparts.com which shows that the only engine oil related sensor, is: “OIL PRESSURE SENDING UNIT OIL LEVEL SENDING UNIT; C300, C300 4-Matic, C350 “… And yes, the reason I said “semi confirms it is because it calls it both, an oil PRESSURE sender, and an oil LEVEL sender.

That part number, by the way is:

001-153-11-32 OIL PRESSURE SENDING UNIT OIL LEVEL SENDING UNIT; C300, C300 4-Matic, C350

The only bad thing about this is that I had a fresh oil change, barely a 1000 miles on it and it appears that if I am replacing the sensor, the oil will have to be drained, …. Or else!

On second thought, and under the circumstances and considering what potential alternatives might creep up, maybe replacing the sensor $30+ in parts and draining the oil isn’t that bad of an outcome.

Thanks again for sharing your knowledge.

Mr.Mango

I converted the BAR numbers to PSI for ease, most people have pressure gauges reading in PSI


Level sender is different than a pressure sender, you can have 15 liters in your oil pan but if your pump isnt creating pressure your in trouble!

Oil pressure sensors are usually located in the side or front of engine blocks. Well above the oil level in the pan so removal can be done without draining the oil or removing the filter.

I would consider this a serious issue, its LIKELY a pressure sensor/switch but you wouldnt want to risk your engine on an assumption! Cheap insurance lol

IGB

I just wanted to provide a sort of a closer, or a "solved" post to tell how this all ended up. As I stated in my 1st post, this all came about as part of my wanting to be ready for a emissions/smog check. Well, I ended up taking the car in and after all was said and done, there was no P0522, at least none that came up on the "official" OBD-11 reader that is used as part of the process to determine whether the vehicle passes the test or not. I even asked the guy (after he signed/transmitted the "Passed" certificate and gave me my receipt) his response was" there were no codes detected on my equipment, not even a past code that had been stored in/cleared from memory recently. It might be that the code reader you used is faulty or it needs a software update of some sort."

Either way, I learned a few things as part of this process. I was able to obtain some references that describe how one would go about testing engine pressure and thought I'd share those details with everyone here.


Component Identification and Specialty Tools



Engine Oil Pressure Testing & Inspection - Detailed Procedure



Pressure Specs - Torque Specs

A.D.S.MANN

Where is oil pressure switch on m272 engine.