Would EML light come on if the front assist is not working?

Yes, in some cases, the Electronic Management Light (EML) or Check Engine Light (CEL) on a 2017 SEAT Leon could come on if there is an issue with the Front Assist system. The Front Assist system is a safety feature that uses sensors and cameras to monitor the road ahead and assist the driver in maintaining a safe following distance and avoiding collisions.

If there is a malfunction or fault detected within the Front Assist system, it could trigger a diagnostic trouble code (DTC) that activates the EML or CEL. Modern vehicles are equipped with complex onboard diagnostic systems that monitor various systems and subsystems for any abnormalities or failures. When a fault is detected, a corresponding trouble code is stored in the vehicle's Engine Control Module (ECM) or other control modules, and the EML or CEL is illuminated to alert the driver.

It's important to note that the EML or CEL can be triggered by a wide range of issues, not just related to the Front Assist system. To determine the exact cause of the warning light, it's recommended to use a diagnostic tool to retrieve the specific trouble code(s) that have been stored in the vehicle's computer. Once you have the trouble code(s), you can refer to the vehicle's service manual or consult with a professional mechanic to diagnose and address the issue correctly.

This guide can help to get the codes:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please go over this guide and get back to us.

Did they do a code scan?

Did they do a CAN scan? This kind of scan goes over the entire car not just the drivetrain. You can get a CAN scanner (Controller Area Network) which will work on most cars from Amazon.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

and

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Here is one for about $99.00 if you need it:

https://amzn.to/3ZixY4v

Please go over this guide and get back to us.