Ok So I bought a 2002 Dodge ram 1500 4x4 with the Infinity Sound System .Someone has apparently replaced the two door speakers with a PowerBass Brand 6x9s . The System Sounds Like a combination of distortion /and or sound of a blown speaker. Neither of rear door speakers work but have original infinity speakers there still. Checked wires by plugging in new fosgate replacements speakers and still no sound from rear doors. Also took a New speaker and Hooked to front passenger door and still sound didn't change Sounds like Distortion /interference or something, I also replaced the stereo head with another original one to see if it changed which it did not the interior dash wiring has not been tampered with still wrapped tight factory. Im confused on what happened or how to fix.

 

Did the stereo system ever work correctly, or has it always had a problem? Do you have an aftermarket head unit?
The previous owner could have installed an aftermarket head unit, then took it out prior to selling the truck.
For troubleshooting steps, check your equalizer controls and ensure you have equal sound levels to all speakers (fade and balance at zero).
If all speakers are getting a signal, then I think you will need to take out the head unit and have a look.
It sounds like your antenna may not be plugged in, or, speakers may not be wired correctly.
Look up video on how to check speaker function and polarity with a battery.
I do not have the Infinity system, but most amps have a light that glows when they are powered on. If your amp is bad, you will not get a signal to your speakers. Bad amp could also result in distortion.
Just a few things to check.