Are you sure the mechanic checked all the connections? Have you checked to make sure none of the wires are crimped? It could be as simple as a bad connection to a seat harness. I remember when I had some interior work done, we forgot to plug the power seat connector in. That immediately tripped the light when we turned the car on. So if there's a loose connection, that may cause intermittent warning lights. I can't even see how the module itself would go bad.