What is the p015d code for the chevy silverado?

Diagnostic trouble code (DTC) P015D on the Chevrolet Silverado (and many other vehicles) indicates that the PCM has found a delayed response time from the upstream oxygen sensor. It's exceedingly likely, in this case, that your O2 sensor has failed, but it may also be the result of bad wiring, a failed or plugged catalytic converter, or other exhaust leaks. If your catalytic converter has not already failed, it's likely that it soon will; you should check over your Silverado quickly, since a bad oxygen sensor can quickly cause other issues that are exponentially more expensive to fix. In the meantime, you'll generally experience poor fuel efficiency and poor engine performance, so in and of itself, P015D is worthy of a quick check.