My "check engine" light just came on but the diagnostics says No Malfunction? on 2000 Mercedes-Benz S430

I do not have a manual. I did check oil level and appears OK. Pleae advise. Thanks!

Asked by for the 2000 Mercedes-Benz S430
Scan for trouble codes using a professional grade scan tool have trouble codes stored, pending codes and "freeze frame" information printed so the trouble codes can be properly diagnosed.
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What diagnostics? Find someone who has a diagnostic tool that can read data on the enhanced side of the PCM not just a generic OB2 code reader.