02 sensor designator

[GTSlookin]

Tried search with no luck on this and was hoping someone has figured this out. I am getting code P0155 2/1 failed heater element.
The 2 means downstream but can not find in the manual which side the 1 means.
Anybody??

 

[dave6666]

1/1 left upstream
1/2 left downstream
2/1 right upstream
2/2 right downstream

 

[GTSlookin]

Thank you dave, much appreciated.

 

[GTSlookin]

The culprit. Got caught up around engine mount somehow and sliced one wire. Was out at local track three weeks ago. Finally worked it's way through.