P0137 and P0157

WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0117, P0118, P0125, or P0128 is not set.
The HO2S 2 is at operating temperature for greater than 90 seconds.
The engine is operating for greater than 5 seconds.
The ignition voltage is greater than 10 volts.
The engine coolant temperature is less than 40°C (104°F) at start-up and the engine coolant temperature was greater than 60°C (140°F) when the ignition was turned OFF last ignition cycle.
The calculated exhaust temperature is greater than 800°C (1472°F).
DTCs P0137 and P0157 run continuously once the above conditions are met.