stalls immediately after starting, shows check engine

Hello, if the engine is not running, you cannot rely on the appearance of a "check engine" light. The light staying on while the engine off would be normal. It is when it stays on when the engine is running that is of interest. That said, check for any diagnostic trouble codes anyway. Your stall is caused by either a lack of fuel delivery, ignition spark, air intake (or too much air), engine compression issues or ignition timing issues. Testing is required to find out what element is not operating at proper specifications.