I have a 2001 cavalier and would like to swap the rear stock speakers with a set of aftermarkets but the connector is a 4 pin and all audio stores i checked carry only a 2 pin. Is there a harness out there for purchase or do I have to splice into the connector?

do you have the monsoon amp setup? look behind the carpet in the trunk on the drivers side for a small little amp, if so follow these codes

Monsoon/amplified system specific:
Black - Left Front Tweeter Output (+)
Yellow - Left Front Tweeter Output (-)
Dark blue - Left Front Midrange Output (+)
Light blue - Left Front Midrange Output (-)

Light green - Right Front Tweeter Output (+)
Purple - Right Front Tweeter Output (-)
Dark green - Right Front Midrange Output (+)
Orange - Right Front Midrange Output (-)

Red - Left Rear Tweeter Output (+)
Purple - Left Rear Tweeter Output (-)
Dark blue/white - Left Subwoofer Output (+)
Light green/black - Left Subwoofer Output (-)

White - Right Rear Tweeter Output (+)
Yellow - Right Rear Tweeter Output (-)
Dark green - Right Subwoofer Output (+)
Light blue/black - Right Subwoofer Output (-)

Yes I do have the amp, thx for the help.

you can also just run new wires from the wiring harness on the deck to the new rear speakers.