I've purchased a Bosch premium O2 sensor kit with SmartLink. It comes with a wiring chart but I have 2 wires that are not on it. My original O2 sensor has a red and yellow wire along with gray and black. Which wires are the heater wires and which wires are the signal and ground?
These 2 links should help you out. These 2 video links give step by step instructions on the wiring of O2 sensors as well as how to install them.
Simple, step-by-step instructions to assemble and install a Bosch Premium Oxygen Sensor with SmartLink ..
O2 or Oxygen Sensor Heater (the 2 grey connectors are the heater +/-)