The transmission light in my 2019 Great Wall Steed stays on has been on for a while

There are a couple of issues here. The first is that your mechanic may not have the correct scanning tool to be able to interrogate the car’s on-board computer to check for fault codes. And without the correct one, you won’t get far down that track. However, it’s worth following that route as it’s the best, most efficient way to find out what’s really going on inside the car.

Ironically, the same scanning tool required will probably also be able to turn the transmission warning light off. But turning the light off is not the solution; you need to know what triggered the warning in the first place and attend to that. Otherwise the light will keep cropping up, regardless of how often you turn it off.

Continuing to drive with a warning light illuminated risks doing more damage to the vehicle in the long run. Something is not right in your car’s driveline and the car knows it. But you’ll need the right mechanic with the right tools to be able to know what the fault is and how to fix it.