That is called the Secondary Air Pump. It will turn the Check Engine Light
When the exhaust is cold, there isn't sufficient air to allow the CAT
(catalytic converter) to do its job, so the secondary air pump is used to
inject additiional clean air so the exhaust will come out clean. After the
CAT heats up, the secondary air pump can be turned OFF because it is no
The secondary air pump will cause the car to fail smog testing, but the
engine won't care that you have it or not. There is no danger to the long
life of the car without the secondary air pump, but you will make more dirty
air for the few minutes that it is used, and you will fail any smog test
that is required before you have it fixed. Well, yoiu will fail the smog
test if the Check Engine Light is ON at the time of testing. The pump's
noise is not always an indicator of failure.
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