How to tell if you have a problem :
If you hear a beeping coming from under the hood of your vehicle. This is a feature which Ford has implemented for diagnosis of the sound symposer system. It may or may not show the DTC's p26DB, p26dd, or p26de. However they will not light up your check engine light. Ford has a few ways of fixing it but one of them just involves leaving it as-is. Ford does have a replacement sound symposer unit as well, however if you are out of warranty, simply unplugging it may be the answer.