I just went through this with someone who has a W124 with the OM602. Happened suddenly and out of the blue. He installed a mechanical gauge setup under the hood and it showed the oil pressure to be fine. The sending unit was bad.

However, I agree with Compress Ignite and 97 SL320. Check all that, but don't panic. I'm seeing more and more sending units fail in the manner that you describe.

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-Louis

'87 300D Anthracite