PO131 error code ?

[DuncanG]

Hi all.
Have a 2010 Aveo 1.6 Auto which seems to run smoothly. Consumption is 9L/100km dropping to 8 on the open road.

Was playing with my ELM327 and it picked up this message of an error?

Any ideas of most likely cause ? Where do I look first without many tools ? Have a voltmeter.

Where is the Heated Oxygen sensor 1, bank 1 ?
Does low voltage mean low or none?

Much obliged

[DuncanG]

Message was " low voltage " ??

[DuncanG]

Anyone know the Bosch number for the sensor ? Trying to buy here in South Africa but they have 8 types...........

[DuncanG]

Went to Bosch who told me that these sensors are often faulty and give incorrect info re fuel mix causing your car to use more.....
Just filled up and my new usage is 7.7 l/100k !!! Exactly what the experts tell me it should be.
Now when the sensor was "working" my consumption was 9/8 ish and is now 7.7 with faulty sensor??
Bosch told me to leave it alone and maybe refit new one only if engine light comes on?
Your thoughts?