93 camry stereo

First, check your wiring to ensure you have it all correct, as it sounds you have cut the factory harness, so use the diagram supplied.

If your wiring is all correct, check your power with a DMM, and see if you are getting constant and switched. Also make sure you have a good connection to ground.

If you don't have power on one of the two, check ALL of your fuses under the dash and under the hood. If you do have power on both, then you should have a fuse on the back of the HU, check that, if its good, then you are down to either a grounding problem or the HU is no good.