Q: The Check Engine Light is on but the scanner shows no codes.

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Check engine light turned on shortly after mechanic checked alternaator and battery voltage with his tool. The mechanic told me the battery (not the IMA battery) is dead after checking the voltage. But I bought a new scanner and it shows no codes and says MIL status is off, although the check engine light is on.

My car has 140000 miles.
My car has an automatic transmission.

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