What does it mean?
This diagnostic code (DTC) is a generic powertrain code, meaning it applies to OBD-II equipped vehicles. Although generic, specific repair steps may vary by make/model.
Basically, it means the downstream oxygen sensor of the catalytic converter on bank 2 detects that the converter isn’t working as efficiently as it should (according to specifications). It’s part of the vehicle’s emission system.
Symptoms
You probably won’t notice any driving issues, although there might be symptoms such as rough/hard cold idle.
Causes
A P0431 code can mean one or more of the following has occurred:
The catalytic converter is no longer working properly
An oxygen sensor isn’t reading (functioning) correctly
There’s an exhaust leak
Possible Solutions
Inspect for exhaust leaks. The next step is to measure the voltage at the bank 2 oxygen sensor. Actually, it would be a good idea to test each O2 oxygen sensor while you’re at it.
One thing to note is that many automobile manufacturers offer longer warranties on emission-related parts. So if you have a newer car but it’s out of its bumper-to-bumper warranty, there might still be a warranty covering this type of issue. Many manufacturers offer a five-year unlimited mileage warranty on these items. It’s worth checking.