I'm getting the following codes on a 2004 XJ8 with 96K miles. I replaced the downstream o2 sensors in an effort to clear codes. But they are still present. Other than the engine light coming on, the vehicle seems to be running smooth. Any input would be appreciated.

P0037HO2S-12 (Bank 1 Sensor 2) Heater Circuit Low InputView Details
P0057HO2S Heater Control Circuit Low (Bank 2, Sensor 2)
P1646Linear O2 Sensor Control Chip (Bank 1)
P1647Linear O2 Sensor Control Chip (Bank 2)