The engine (compression) brake shuts itself off if the exhaust flap or its actuator is faulty. On a descent this immediately shifts the whole braking load to the service brakes — not something you do with a loaded truck going downhill.
The answer depends on the code, not the light. A yellow light is a warning; a red one means do not move. But even under a yellow light there are faults that require stopping right away — low oil pressure, overheating, lost brake pressure. Enter the code — the reference will tell you plainly whether to keep driving or stop.
Know the code number? Type it into the search — or paste the whole list from the scanner and we will show which fault is the real one.