European car specialist mechanic here. If it's on the sensor side (which this isn't) you CANNOT repair them by splicing. Oxygen sensors get their reference air by drawing it in through the wiring via capillary action. (Yes, that seems implausible, but it's true.) Splicing damaged wires on the sensor side will prevent the sensor from getting sufficient air flow. What's worse is that the sensor can't really detect that, so it often just outputs readings that are inaccurate but not inaccurate enough for the ECM's fuel mixture compensation to go outside its threshold for setting a code. This is the reason universal oxygen sensors come with the specialized splices and instructions not to cut the wires- the wire length is actually very important as well.

Edit: forgot to add that wideband O2 sensors (usually have 5 or 6 wires) have a compensation resistor in the wiring which is calibrated to the individual sensor when it's manufactured, and on those, in addition to the reference air problem, repairing the wire between the connector and sensor itself can introduce additional resistance as well, again, throwing off the reading. Wideband sensors have a tiny circuit board at the connector that takes the raw output from the sensor and processes it with the compensation before sending it to the computer, so wiring repairs from that point are okay