Speakers were working than all of them stopped working on 03 dodge caravan radio works

Most likely a blown fuse or relay

Try the speakers cable with a different deck

There is a fault in the player most likely the heads need a clean a tape con be obtained to do this .

Unscrew the suspected speaker and use a DVOM to check that values are correct or???......Check for juice at the + terminal of speaker with radio on,probably a open circuit,check your grounds....It is possible the output is completely fried;will appear that everything is okay,but no output......

Will the color code do, or do you need the actual wiring diagram?
1997 Dodge Caravan Car Radio Stereo Audio Wiring Diagram
Car Radio Constant 12v+ Wire: Pink
Car Radio Switched 12v+ Wire: Red/White
Car Radio Ground Wire: Chassis
Car Radio Illumination Wire: Black/Yellow
Car Stereo Dimmer Wire: N/A
Car Stereo Antenna Trigger: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Green
Left Front Speaker Negative Wire (-): Brown/Red
Right Front Speaker Positive Wire (+): Violet
Right Front Speaker Negative Wire (-): Blue/Red
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Brown/Yellow
Left Rear Speaker Negative Wire (-): Brown/Light Blue
Right Rear Speaker Positive Wire (+): Blue/Orange
Right Rear Speaker Negative Wire (-): Blue/White

Radio display plug is faulty.

1996 Dodge Caravan Car Radio Stereo Audio Wiring Diagram
Car Radio Constant 12v+ Wire: Pink
Car Radio Switched 12v+ Wire: Red/White
Car Radio Ground Wire: Chassis
Car Radio Illumination Wire: Black/Yellow
Car Stereo Dimmer Wire: N/A
Car Stereo Antenna Trigger: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Green
Left Front Speaker Negative Wire (-): Brown/Red
Right Front Speaker Positive Wire (+): Violet
Right Front Speaker Negative Wire (-): Blue/Red
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Brown/Yellow
Left Rear Speaker Negative Wire (-): Brown/Light Blue
Right Rear Speaker Positive Wire (+): Blue/Orange
Right Rear Speaker Negative Wire (-): Blue/White

Check the fuse box under the hood. It should be located on the drivers side. Open it up and check around for the radio fuse. Most likely labeled as "ACC" which is short for accessorie. It should be a 15 AMP fuse. Last winter my radio blew out as well and I check the fuse box and replaced the fuse and now it works fine. The fuse was burnt beyond believe though. If you havent already fixed the problem I hope this helps.

Here's the link and I'm sure you will get the solution of your problem
https://www.reliable-store.com/products/2003-2007-dodge-caravan-service-repair-manual-instant-download

The stock radio? Or is it something someone put in there?
I would pull the radio out and check to make sure the harness is fully engaged in the back of the radio.