If you don't find an obvious problem with the wires or connector, you could try swapping the sensor with the upstream sensor from the other side. If the error code follows the sensor, then you know the sensor is the issue.

Also double check that the upstream and downstream sensors are plugged into the correct connectors.

Also important is that the upstream and downstream sensors are different part numbers, so if an upstream and downstream sensor got swapped during the install, this could cause problems. The install guide specifically said to arrange the sensors by connector color, but I found that the connector colors were opposite on one side vs the other in stock form. One side had a black connector upstream, white connector downstream, while the other side had white upstream and black downstream. I simply kept all of my O2 sensors in the same arrangement when I moved them from the stock pipes to the Prodigy pipes, disregarding the connector colors. If your connectors were arranged based on connector color, you may have an upstream/downstream swap.

Install guide says that upstream sensors have black connectors, and downstream are white. My driver side sensors were opposite. If your problem is on the driver side, and your upstream driver sensor has a black connector, try swapping the driver side upstream and downstream connectors.