This may be somewhere around here already, but I finally fixed the flashing SYS light caused by my aftermarket stereo. All told it was about a $5 project.
Heat shrink tubing that fit over 20 gauge wire
One red Male quick disconnect (yes this one is blue, you need the red one)
One blue "T Tap"
Two "1k, 1/2 Watt" resistors (Radio Shack)
I did the easiest thing I could fine, but it still required cutting the factory harness.
I first took the red quick disconnect and the two resistors and crimped them together. The red disconnect is for 20 gauge wire but the leads on the resistor are much thinner then that so both leads will fit inside the crimp of the disconnect with no problem. Both resistor should be sticking out of the disconnect when finished like a 'Y'.
I then cut the GRAY/BLACK STRIPE and the PURPLE/WHITE STRIPE wires from the factory harness and stripped the ends about 1/2 inch. I put 1 piece heat shrink tubing over each of the wires. The tubing should be long enough to cover the splice we are about to make plus resistor completely all the way to the crimp on the disconnect. This makes it a little nicer and less likely to short out something.
Then twist one wire to one of the resistors and the other wire to the other resistor. You can solder if you want, but I don't think a butt connector will crimp well to the thin resistor lead. I just twisted them together.
I pushed the heat shrink tubing over each assembly from the wire splice all the way up to the end of the disconnect and heated it. I think this creates a pretty good connection.
Last is to crimp the "T Tap" onto the red power lead. Make sure the tap is within about a foot of the radio. The wires that you spliced eariler aren't very long. Anyway this is an ignition switched power connection. Once you crimp the tap into place just plug the disconnect into the T-Tap and you are done.
Hopefully there is no SYS light after this.