Volvo: 2001 volvo s40, 2001 volvo s40, volvo s40

Question
The check engine light on my daughters s40 will not reset. the codes came back as O2 sensor, thermostat,and turbo boost. I had the items replaced and it cleared the codes except the turbo boost code. After the electrical part for the boost code was replaced the light went out. On the way home, the engine light came on again and when the auto zone tech did the test, it is coming up as the turbo boost again. Any idea what is wrong??

Answer
Marc,
There must be something like the electrical or vac line that go to the boost control that are not allowing it to work properly. Check those and see what you can find. Since there is so many possibilities you may consider taking the car to the dealer or Volvo shop and have them look it over. They will be more equipped to test these components.