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Q: just replaced motor in 2007 mazda 3 check engine light won't go out. what could cause this.

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Looking at buying Mazda 3 , 2007 runs and drives perfect owner had engine replaced and the check engine light won't go out. Any thoughts?

My car has 107000 miles.
My car has an automatic transmission.

The check engine light comes on to indicate that the Electronic Control Unit (ECU) has detected a fault in the engine management system. When that happens, there will be a code stored to represent the malfunction. The codes can be read with the appropriate scanning equipment and a technician interprets the code and decides what steps to take. It’s not uncommon to see a check engine light after an engine replacement, often it means that the engine wiring harness wasn’t hooked up completely right on the first try. But the light won’t go out until the fault is repaired and the ECU cleared of codes. That said, I’d be wary of a car that needed an engine replacement. Often that happens because the car was poorly maintained, and that can mean there might be other problems lurking as well. For a little peace of mind, you might contact Your Mechanic for a pre-purchase inspection. They can send a technician to the location of the car to check it out for you and let you know what you can expect from the car.

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