All Bosch 4-wire sensors have a black wire for the signal, a gray wire for ground and 2 white wires for the heater. Note: the wire colors and functions on non-Bosch sensors are not necessarily the same as on Bosch sensors.
Bosch has created an aftermarket universal heated oxygen sensor program. These sensors meet OEM operating requirements and have a patented connector system easing installation. This connector system has been proven to be watertight, protect against contamination, and withstand the effects of extreme temperatures and engine vibration. Currently Bosch offers 12 different 4 wire sensors and 2 different 3 wire sensors to provide the closest match to OEM sensor performance. See the Technical Info tab for a diagram of the connector system, featuring special high temperature Posi-Lock® connectors.