I believe the temp it is designed to run at, is for optimum fuel economy, and oil life. A cooler thermostat may jeopardize some fuel economy. I can't find any specific literature on the subject to either support, or condemn the use of a different thermostat. In certain cases, you may set fault code P0125 if the function of the system is altered enough that it meets fault criteria. I have included the info on that code.
DTC P0125 Engine Coolant Temperature (ECT) Insufficient for Closed Loop Fuel Control
Circuit Description
The controls module monitors the engine coolant temperature (ECT) sensor and engine run time in order to determine how long it takes the ECT to reach the coolant temperature required for Closed Loop operation. DTC P0125 sets if the control module determines that the ECT does not reach a minimum coolant temperature required for Closed Loop operation in a specified amount of time.
Conditions for Running the DTC
†The engine is running.
†No active ECT sensor DTCs
†No active intake air temperature (IAT) sensor DTCs
†The IAT is more than -40°C (-40°F).
†The ECT is more than -40°C (-40° F).
†The start-up ECT is 40°C (104° F) or less.
Closed Loop Test
†Start-up ECT near -40°C (-40° F)
- Accumulated air flow since start is more than 9,000 grams
- Accumulated idle time is less than 360 seconds
†Start-up ECT near -7°C (+20°F)
- Accumulated air flow since start is more than 5,500 grams
- Accumulated idle time is less than 225 seconds
†Start-up ECT near 10°C (50°F)
- Accumulated air flow since start is more than 2,000 grams
- Accumulated idle time is less than 90 seconds
Conditions for Setting the DTC
†The Closed Loop coolant temperature is not reached within a predetermined time. The maximum allowable time depends on the start-up coolant temperature and the amount of air flow into the engine.
†Start-up ECT near -40°C (-40°F)
ECT less than 20°C (68°F) after 8 minutes
†Start-up ECT near -7°C (20°F)
ECT less than 20°C (68°F) after 5 minutes
†Start-up ECT near 10°C (50° F)
ECT less than 20°C (68°F) after 2 minutes
Action Taken When the DTC Sets
†The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles.
†The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool Freeze Frame/Failure Records.
Thursday, July 8th, 2021 AT 9:27 AM
(Merged)