P015D

Had the check engine light come on today. Hooked up my cheap little ODB2 reader, and got a P015D error, with a P015C pending. I know these are Sensor Delayed Response- Rich to Lean for the O2 sensor. But what how do I diagnose if it's a failed sensor, catalytic converter, or a dirty fuel injector?

How would you guys attack this? What's the most likely scenario? Should I just assume it's a failed sensor and replace it?

2012 DBSB 4.0 PreRunner with 150K miles. Everything stock except the transmission.

Thanks in advance.

 

When those codes set and no other codes or driveablity problems are occurring it's almost always an O2/AFR sensor that is getting "lazy" usually any other problems would set other codes in addition to the slow response codes.
Verify you have no exhaust leaks at or near the sensor.
Bank 2 Sensor 1 is Left (Driver's) Side upstream.
If you do end up replacing the sensor make sure you go with a Denso sensor of the correct part number and beware of counterfeits on Amazon and Ebay.

 

I appreciate the feedback.