Troubleshooting: Oil Level Warning - PeachParts Mercedes-Benz Forum

anghrist · #1 09-30-2010, 05:02 PM

Hey folks,

I have a 02/1999 W210 E300 TurboDiesel that keeps giving me a check oil level warning at aproximately one minute after cranking. I'm in the process of tracing wiring to test continuity.

I was wondering if anyone out there with a similar model with a known working oil level sender and wiring could perform a troubleshooting test for me. Disconnect your oil level sender cable and then turn the engine on and time how long it takes to get a warning alarm. I would do this on my car, but without knowing if this simply indicates an open loop somewhere, I would get nowhere.

Thanks in advance.

Josh

69shovlhed · #2 09-30-2010, 07:14 PM

i don't remember , but if its the sender that bolts into the lh side of the oil pan, those do fail sometimes. if its hooked up correctly, i'd be inclined to just replace it at my next oil change.

anghrist · #3 10-01-2010, 01:46 PM

I've already replaced the sender. I think I have a break wire going to the sender. Trying to verify.

bustedbenz · #4 10-01-2010, 02:07 PM

I COULD BE WRONG. I usually am.

But I think these oil level warnings ground to signal low oil. So if you have a broken wire that is not touching anything, the symptom should be NEVER getting a low oil light... *I Think*. I think it has to be a closed circuit to light the warning light. So what you more likely have is a wire grounding out to the chassis/engine through a hole in its insulation.

If I'm 100% wrong and 180 degrees backwards on this, then you're right that a broken wire would be illuminating your light. Somebody correct me on this if I got it backwards.

The 1 minute delay is likely the fact that the thing is configured to wait 1 minute after the switch says "low oil" before illuminating the light to compensate for the fact that the oil may sling away from the sensor every time you turn right or left (whichever it is) and you don't want the light flickering constantly.

Either way it's probably a wire problem. But disconnecting *I THINK* will simply result in never getting an oil warning.

anghrist · #5 10-01-2010, 03:35 PM

Quote:

Originally Posted by bustedbenz

I COULD BE WRONG. I usually am.

But I think these oil level warnings ground to signal low oil. So if you have a broken wire that is not touching anything, the symptom should be NEVER getting a low oil light... *I Think*. I think it has to be a closed circuit to light the warning light. So what you more likely have is a wire grounding out to the chassis/engine through a hole in its insulation.

If I'm 100% wrong and 180 degrees backwards on this, then you're right that a broken wire would be illuminating your light. Somebody correct me on this if I got it backwards.

The 1 minute delay is likely the fact that the thing is configured to wait 1 minute after the switch says "low oil" before illuminating the light to compensate for the fact that the oil may sling away from the sensor every time you turn right or left (whichever it is) and you don't want the light flickering constantly.

Either way it's probably a wire problem. But disconnecting *I THINK* will simply result in never getting an oil warning.

I'm not certain, but that is not how this system appears to work. The FSM mentions that the Oil Level Sensor is connected to the IFI Control Module (N3/7) which communicates the signal to the multifunction display viw the CAN bus. Not as simple as I would perfer. There are at least two possibilities: 0 volts or 5 volts as far as I've been able to tell. I will double check the function of the old sensor and let you know how this works.

ah-kay · #6 10-01-2010, 05:25 PM

There is only 1 wire going to the sensor. It can only be floating or ground to chassis. When it is floating, light is off. When it is grounded, light comes on. It cannot get simpler than that.

The grounded signal may go through a computer to debounce it to stop the light from flickering often. The concept is the same for most sensor/switch detection.