IP = Instrument Panel
The way to check any splice pack, besides any visible melting or charred appearance, is to check the individual wires for continuity with a multimeter.
Same color wires *should* be internally connected within the splice pack, as that is what it is for. I emphasize "should" because that is usually where they fail.
In the case of the S301 splice pack, the purple (violet) wires should measure zero (or very near zero) resistance between each other. Use a digital multimeter on the diode or continuity setting and it should beep or show zero on the screen. If your meter does not have a diode function, use the ohms function and verify the reading between each wire is zero or very near zero.
If there are any dubious readings on wires that should be connected within the splice pack, cut them at the splice pack, peel off some insulation at the ends, wrap them together tightly and install a wire connector on the end. Be sure to cover the connection with electrical tape afterwards, for extra protection.
*** Be 100% certain that the wires you connect are indeed, meant to be connected. Check and re-check the diagram before you connect any wires together. ***
Below is a diagram of the inner connections of the S301 splice pack.