I work as an auto tech- I replace these O2 sensors all the time (yes, checking the wiring harness too). My own personal car just threw a P0135 error code indicating: Bank1 Sensor1 Heater Circuit Malfunction, Oxygen Sensor.
I am trying to learn here so please correct me where my understanding is wrong.
Basically the ECM throws the code if it thinks that the O2 sensor is not heating up quickly enough based on checking it against the coolant temperature. The whole purpose of this being to allow the computer to switch from open loop to closed loop operation sooner for efficiency. When the computer throws this code, the O2 sensor will still work once the vehicle is at operating temperature, but it won't do what it needs to do from a cold start.
I notice absolutely no difference in driveability, therefore I believe I am still operating in closed loop.
Now here is my question: is there any damage that can be caused by allowing this to run? We're talking about carbon deposits on the cylinders/destroying the cat as if it were a totally failed sensor- I don't believe I run this risk because I am still in closed loop and because this is my own POV I just want to make sure. Is this correct?
The reason I ask is because my tools and shop are in another city and I have work to do here so I won't be there for another two days or so (with me still driving extensively). If this were a customer, I would have no problem telling them not to worry; shows the difference in perspectives when the tables have turned.
Thanks for the help,
Techniker