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1999 E300TD: 417,000 kms. Parked for the winter. 2002 Golf TDI, 470,000kms, winter beater
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Hi Everyone,

I have looked for a decent write-up regarding the function of the low oil level sensor, in my case on an 1999 E300TD with OM606 (from what I have read, this will also apply to many cars up to 2000, then apparently they went to a different system), but couldn't find anything really useful as to how to test the level sensor, and circuit for proper function.

First of all, it is a single wire system, thus it can only perform two functions. "Oil level below minimum = warning message", or "oil level not below minimum = no warning". The engine must be running, otherwise no message ever.

I did this during an oil change, car level, oil at full dipstick, using a digital multimeter.

Car running, pull the connector off of the level sensor. After about 15 seconds, I got the message of oil level below minimum. Thus, the car side is working; capable of producing the message. Time to shut car off.

Next I put a multimeter to the pin of the level sensor, and the other lead to ground (the oil pan in this case). The level switch is closed (no resistance to ground).

Then I drained all oil. Now the multimeter showed an open switch (infinite resistance).

I am not sure at which level the switch makes: I added 5 liters of oil, and the switch was closed.

Hope this helps someone, it only takes a few minutes to check while doing an oil change.

Last but not least, I got onto checking this because I had recently seen an add for a 1998 E300TD for sale with a seized engine. According to the add, it blew one of the oil cooler flex lines, and all oil went down the left side of the car and onto the road. I wandered if he didn't get the message, or if he ignored it. I never called the seller, but it did make me function check mine.

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