The check engine light is SUPPOSED to light on startup. That's the bulb check.

If it remains on, then you have a problem.

You can't just turn the light offf, you have to fix the problem.

The light is indication the car's computer has "stored a code" describing generally what the problem is.

You can get a code reader to see for yourself, but the reader doesn't fix the problem.

Government emissions testing involves this same reading of codes, and if there are any, you fail.

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Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles