Have a question that I need help to answer. What is the black box that lives on top of the spare tire and you can see in the picture it has 2 hoses coming out of it? The reason why I am asking is my Ascent was sitting in the garage and I heard a strange noise coming from this exact area. Now the car had not been running for at least 4 hours and moment I hoped into the car and turning the ignition on the noise stopped. So what is that little black box and is it suppose to come on randomly while the car is off just sitting still?
The sound is normal and part of a pressure test for the fuel system. From the manual:
You may hear a noise from under the
vehicle approximately 5 to 10 hours
after the engine is turned off. However,
this does not indicate a malfunction.
This noise is caused by the operation
of the fuel evaporation leakage checking
system and is normal. The noise
will stop after approximately 15 minutes.