When this happened on mine it turned out to be a blown speaker. Remove the door trim ( a couple of screws and the use of a forked trim remover). If you're careful you will be able to re-use the plastic attachment plugs. If not, buy a few at NAPA or similar. At the dealer you will need a mortgage. Remove the speaker. Pull the two spade connectors off the speaker. Put an ohm-meter on low range across the two contacts on the speaker. It should be a small number of ohms, perhaps 8. If it shows infinite resistance, the speaker circuit inside the speaker has blown, and the speaker will need to be replaced. If you want a cheap job, Wal-Mart sells the right size as a pair (Jensen, I think), so you and your pal could have one each! If yours are Infinity speakers, with the attached amplifier, that's more complex, but it can be transferred without too much trouble. Good luck. Nick.