What happens to a three wire O2 sensor if it is wired in wrong?

A three-wire O2 sensor typically has a signal wire, a ground wire, and a heater wire. If the signal wire and the ground wire are swapped, the O2 sensor will provide an incorrect signal to the engine control unit (ECU), which can cause the engine to run poorly or even damage the catalytic converter. If the heater wire is not connected or is shorted to ground, the O2 sensor will not be able to heat up and will not provide a signal to the ECU.