O2 sensor wiring

Only the rear O2 sensors have 4 wires because they are narrow band sensors. On these ones, usually, grey wire is ground, black wire is signal and white wires are for the heater.

The front O2 sensors have 6 (SIX) wires because they are wideband sensors. They are much more complex to diagnose because they need the dedicated electronic stage in the Motronic to work properly. Though the heater can be tested on the white and grey or blue wires (Bosch colors).

Unfortunately, the 360 does not make accessible the front sensors data as part of the OBD2 parameters. It's a pity!

 

Here is a link with some info about wiring and connectors for Bosch wideband sensors :

http://wbo2.com/cable/lsuconns.htm

If you have some concerns with the heater, you should check it with an ohmeter between the white and grey wires. Around 12 -14 ohms should be a realistic value in cold conditions.