if by bass cutting out you mean the bose sub behind your seat is cutting in and out or poping like a blown speaker you might find that the small sub amp bolted next to the sub is faulty ,remove speaker cover remove sub and disconnect ,loosen the 2x bolts you can see nearer the seat belt side and lift off the little amp and withdraw it out the sub speaker hole ,it can then be unplugged flip it over and remove the 4 small screws to remove the black plastic case the silver covers can then be prised open and off like a book (just note for refit how they are) then look on the circuit board for a small grey box (which is a relay) near the back next you could try flipping it over and reflowing the 5 solder joints which affix it to the board but i have found that does not allways have the desired effect but however if you then find a very strong piece of adehsive backed foam and cut to the size of the top of the relay the firmer the better and stick it on top ,it needs to be raised higher than the level of the silver covers so that when you replace them it effectivly pushes down hard on the relay if you then screw it all back together it will be permanantly under firm pressure ,refit the lot and 9 times out of 10 it will cure the problem sub will work without issue ......let me know