First of all thank you . My daughter just came by with the car fully warmed up with outside air temp of 15'. The 195' thermostat installed yesterday had the engine running at 192' -196' . The code for low temp is not on ( it was running at 189' with old thermostat and taking 3-4 days of driving before throwing low temp code) at this time . We'll see in 3-4 days ?? But now a new old problem is back . The code PO137 bank 1 sensor 2 is on along with check engine light . I had this code gone before by replacing #1 O2 sensor with a genuine AC Delco sensor . I still have a universal O2 sensor in the #2 position . Maybe replace the #2 universal with a genuine AC Delco next ?