CaliBenzDriver

R-Value unlikely infinite.


RESISTOR SETTINGS

Your DVM is not auto-ranging.
meaning you need to select expected value range

How:
Start high in Meg-Ohms then switch down towards min.

I would expect R-value out of circuit may be around 1k to 200kR... let's measure as reference.

The value to us is meaningless but the ECU when it sees the condition recognizes it as "low oil".

When R is infinite it means circuit defective by self-check R. Open is the abnormal fail-safe value.

JettaRed

iTrader: (1)

My DVM was set to 200 ohms. The closed switch readings for both the removed level sensor switch and the installed level sensor switch were the same, 0.8 ohms.

I mentioned @BenzNinja because if my IC needs to be re-initialized, it can only be done by someone that has access to Mercedes' servers.

CaliBenzDriver

You're right,
the WHOLE TIPPING POINT remains :
Sensor Level faulty BEFORE ECU
vs.
Level data becomes faulty AFTER ECU.


I hear you have good reasons to be leaning towards IC DISPLAY issue and we've seen your SCM may well be acting faulty.

It's interesting to see that IC-Display spends its time reading the ECU oil level data to display it.
Meaning the (known reliable) "A1 Module: Instrument Cluster" heavily relies on CAN-B to read data from ECU over CAN-C through busy CGW.

JettaRed

iTrader: (1)

Actually, the IC seems to control a lot of stuff. I go back to the list of errors (which I didn't list before but will now). Because I tried to enable oil level reporting on the IC menu, I may have hosed up other stuff. @BenzNinja likes to remind me that I shouldn't be futzing with stuff I don't fully know about. Also, these inexpensive scan tools can get you in trouble if you don't know what you are doing. Anyway, here are the errors. As you can see, they have IC malfunction in common. If I messed up the coding (as indicated in DTC C073600), that could be the cause of all of this.

CaliBenzDriver

Report shows:


these errors involving "A1-IC" may be transient when you code your IC and the module is unavailable during self-reboot.


The Mercedes A1 Module used to act as chassis GATEWAY but now CGW has been merged with Bosch F-SAM.

Display remains well networked all over because the architecture has not changed much... busy traffic bandwidth.


If anything this stresses the importance of getting configuration BACKUPS.... we are all guilty.

JettaRed

iTrader: (1)

This is an interesting video. Not my engine, but the oil level switch looks the same. Only, in the M276 there is no bracket, per se, to replace.

JettaRed

iTrader: (1)

Since doing the continuity testing as described by @S-Prihadi I have driven the car several times for distances and time greater than before when the warning message to Check Engine Oil would appear without it appearing. I don't know if disconnecting connector X26 No.4 and then checking continuity at Pin 13 on both sides of the connector (male and female) may have caused a reset of whatever condition was causing the problem, much like the chassis reset that @CaliBenzDriver always talks about. Hmmmm! Makes me wonder.

CaliBenzDriver

JR, you have the pulse of things, nothing MB is easy. This is like the chassis voltage YoYo: it's when you think you got it cornered that it comes back.

It's upsetting when so many systems disfunction.
At least your engine does not limp-mode when oil sensor goes missing AND you have the faithful dipstick as backup.

Wait to Reboot for a while or until bug shows up.
Hope it stays fixed
​​​​​​

S-Prihadi

Lets hope its just one of those bad-intermittent-contact bug.

JettaRed

iTrader: (1)

The interesting thing about the video above is that the first step is to physically check the oil level to determine if the warning can be dismissed (ignored). However, in the case in the video, it was a matter of everything working properly but that the oil level sensor sat too high in the oil and if you didn't fill to the max level you may get the warning. In my case either there needed to be some reset to the ECU logic or I need the IC re-initialized. When checking continuity on the ECU side of the X26, grounding pin 13 may have effectively reset something. Keeping fingers crossed. 🤞