Gotcha. As others have said, it would helpful to know year and trim level of your truck. Also describe your radio headunit. Is it a 12" screen, an 8.4" screen, or a 5" screen. If you can't pinpoint it using the AlphaOBD, you'll need to test the wiring. IMO it's either one of three things: 1) a problem in the headunit/program, 2) a problem in the wiring (less likely), 3) a problem with all four speakers (unlikely). I say unlikely for the last two because it's hard to believe that all four speakers are not just blown but dead, and that the wiring to all four speakers is bad. It could be a problem from the headunit to the ANC (if you have one), which is why it's still a possibility.