Might help to pull the plug and see if it's even getting power lol! I highly doubt something that is only manipulating what the ecu reads is capable of harming it.

Who spliced the wires? Some of the worst electrical hack jobs I've ever seen were on piggybacks. I'd recommend making or buying a harness with OEM connectors, just like a conversion harness, rather than cutting and splicing into the main ECU harness. it makes everything plug and play and easily put back to stock. Solder and heat shrink is your friend, not twisting wires and wrapping in electrical tape.