Premium / Non-Premium
The biggest thing to know is whether it is a premium sound radio or not. The premium sound radios use an external amplifier to power the speakers. The non-premium units or “base” radios have an amplifier built in to the radio. They don’t interchange with each other. All of the CDR and PAC radios are premium only. All of the ESR radios without a cassette player are not premium sound. The confusing model is the ESR/C because those can be both. A simple look at the connectors in your vehicle will let you know what you have.
Premium sound equipped vehicles have 1 rectangular plug and 1 smaller square plug. They also might have additional connectors for remote cd players, cd changer, etc.
Non-Premium radios use 2 long rectangular plugs.
