除了vsv外，control modular, egr valve 应该是容易换的。 都看得见，摸得到。

A vacuum-controlled EGR valve is easy to test with a hand-held vacuum pump (see the image). If the EGR valve opens and the vacuum holds for more than a minute, the EGR valve works. If a vacuum diaphragm inside the EGR valve is leaking, the vacuum will drop. Once the vacuum is released, the valve should close fully. Vacuum lines and the control solenoid must be tested too. In older Toyota vehicles, for example, a failed EGR control solenoid (VSV) can cause the code P0401. Replacing the VSV is a lot cheaper repair.