I've been getting poor city fuel mileage (fine on the highway) and the following engine codes:

============1==============
P0141
Raw code: 0141
ECU: Engine control unit
Status: Confirmed
OBDII: Heated oxygen sensor (HO2S) 2, bank 1, heater control - circuit malfunction
Mini: O2 Sensor Heater Circuit

============2==============
P0136
Raw code: 0136
ECU: Engine control unit
Status: Confirmed
OBDII: Heated oxygen sensor (HO2S) 2, bank 1 - circuit malfunction
Mini: O2 Sensor Circuit

============3==============


I got quoted to replace "both sensors" at $380. Is this is a fair price?

I didn't really understand the mechanic's explanation of why both need to be replaced. As far as I saw from the codes, they are all related to 1 specific sensor.

Thanks

 

The top sensor is pretty easy to access, so you could replace it yourself for the cost of an O2 socket and sensor

 

O2 sensors performance degrades gradually over time, so Mini recommends replacing them at certain intervals (don't recall off the top of my head but I think it's like 100kmiles). So if your car has a lot of miles it might be worth replacing both.
$380 sounds reasonable depending on your local cost of living. The sensors are about $100 each so that's $180 in labor, taxes, etc.
They're not terribly difficult to replace - assuming they're not rusted in place, then the job really becomes a chore.

 

Appreciate the perspectives @mrbean @njaremka The car is nearing 100k so I'm thinking to save myself the time and just have the both replaced. Sounds like a fair price. Thank you!