The Passat spent another day in the shop. The final determination - unknown problem. They checked it high and low, hooked it up to the computer and couldn't find anything wrong. So I went to pick it up and take it to the Volkswagen dealer sometime soon. I'd also asked them to look at the oil sender because the wires had been weak and broken. Volkswagen's buy extra parts plan starts with an oil pressure sender unit that has unreasonably fragile connections, and worse yet no way to fix it. They made a way and attached the dangling wires. I thanked the shop guys and got in the car to leave. Amazingly there was NO check engine light. It would appear that a broken wire to the oil sender is reported by saying there is an emissions problem. Who would know... I wonder if a flat tire is reported as an electrical problem.