I was replacing the Mass Air Flow sensor on my 2004 Volvo S60 T5 this evening. As I removed the lid from the air filter box, I noticed a sensor near the box “pop” off. The spot that it “popped” from had a spring sticking out of a porthole. I can see that the sensor popped off due to the housing becoming brittle due to age and the part of the housing that latches onto little tabs at the base have simply broken. I have included pictures of the sensor removed from the car, and pictures of the sensor being held into place with a couple of zip ties. Can anyone help me identify this sensor, and explain its purpose?

 

That sir, would be your brake vacuum pump switch. Not exactly a sensor but needed to help the brakes on cold start.

 

Thank you damien360!

 

How crucial is this pump? Mine broke and I wonder how fast I need to replace it.

 

It helps with breaking in cold starts. Once the engine builds vacuum it should be ok. But it is a vacuum leak so it could throw a check engine light. A broken switch could possibly burn out the vacuum pump so you might have to replace that as well.

 

Thank you damien360 for the info

 

Mine was broken too and I lost spring, guess this needs replaced.