An owner of Mercedes S280 sedan with W220 chassis says: " It is very
ofen to see that engine oil is less than 2L on the car meter
multi-function display. "
When I took the car, I pulled out the dipstick to check the car's oil level height is normal or not with V2015.05 MB SD Connect Compact 4
displaying oil Ievel temperature oil position and temperature. After
asking the owner, I got that the car has been diagnosed in several
large-scale diagnostic repair shops and they say the oil level sensor is
faulty. And the sensor has been replaced in the two repair shop. Then
they regarded the issue resolved because of the change of the sensor,
but before long the multi-function meter will display on the oil than
2L.
Given the previously encountered failure and the solutions of
replacing the oil level sensor, I decided to replace an oil level
sensor. I then add the right amount of oil to refit after commissioning;
the multifunction meter still shows the oil is less than 2L.
Apparently, the problem was not oil level sensor. At this point I had
some doubts that the car's mileage is not too much, but we had to
consider whether there are some problem in the oil level sensor to the
line between the right of the ME control module group or not. So it was
measured with a multimeter oil level sensor 7 to 3 lead right side ME
computer, which three lines are brownish-black, gray-blue and red and
green. The measurements showed that each of the wires are normal, no
breaks in. Is ME computer will be a problem? Of course, we can only
think so, but must put it in the end. To accurately determine the fault,
I have made a measurement of the line, but I still found no problems.
Then, I continue to check the oil level sensor connector between right
and SAM, but I found no bent pin, or damage to the phenomenon. The test
sensor supply voltage is normal, with an oscilloscope measurement signal
normal.
At that time, I was puzzled because if there is any
problem on the multi-function display, ME computer, or CANBUS, MB SD
Connect Compact 4 Wireless Star Diagnosis should be detected; however,
we considered maybe the line virtual access are with some problems.
So
we put the wires on the connector pin with a multimeter block to
measure the voltage change between the voltage sensor and the right side
of the SAM. The results were also found no abnormalities. And when we
will lead with a pin inserted into the line terminal, the findings on
the MB STAR multiplexer （I got the 2015.05 verison）showed that flashing
on the black box of oil position, temperature and quality of the sensor
and multi-function instrument dashboard also from time to time. If we
remove pin lead and plug it directly, the fault would appear again. If
we sway it back and forth by hand, the harness fault appear sometimes.
Therefore, we drew a conclusion that the three pins on the right side of
the engine computer connected to the oil position sensor B40 in the
gray-blue line sometimes occurred virtual connection. After we dealt
with it, the fault completely ruled out.
Having ruled out of the
car after the failure, I got that in fact line virtual access problems
on all types of vehicles are occurred relatively common, but it is
relatively rare, in the Mercedes-Benz W220 chassis of the car because
the level of technology of the car could not really make this failure
occur. And because STAR diagnostic misled that the back and forth motion
of the harness make the plug hard to change sometimes, and our fault
diagnosis brought some resistance. It also illustrates that, no matter
what kind of vehicle, it is very necessary to have the conventional
fault diagnosis and logical thinking.
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