A powertrain control module is a printed circuit board computer housed in a heavy duty case that can withstand the extremes of temperatures normally experienced inside a vehicle's engine. The module constantly sends electronic signals to all of the different components in the engine, and tests the temperature and airflow around them, to check on the status of their operation. When a component is not working properly, the module turns on the "check engine light" on your vehicle's dashboard.
Take your vehicle in to Autozone of Shucks and have them perform an electrical diagnosis, thie is free and it will also either reconfirm what tha mechanic mentioed or point you in a new direction.
There are other reasons the "check engine" light will appear. For example, a dirreft O2 may be malfunctioning, your catalytic converter may also be mafunctioning or damaged. It coulde also be improper air/fuel mixture and/or fluaty fuse.
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