So my car was shaking and would not run so I took it to a mechanic and he said they did a complete tune-up including an oil change throttle body clean up spark plugs air filter air filter replacement ignition coil #3 my car still leaking and my check engine light is on. He claims all this will take the check engine light on so I took it back my car still leaking and my check engine light is on. He claims all this will take the check engine light on so I took it back to him. He couldn’t figure out why it was on so I took it to another mechanic. They told me since my car is old they don’t have a machine to do a diagnostic so just to leave it there for a couple hours so he could figure out what it was  so when I went to pick it up, he didn’t know what it was and told me as long as it’s drivable that should be fine. My concern is why is the check engine light on still ? so when I went to pick it up, he didn’t know what it was and told me as long as it’s drivable that should be fine. My concern is why is the check engine light on still 

I have a 2001 BMWi mile on it 153758