Time To Closed Loop Monitor
For the 2015 MY, an additional monitor was added to ensure that the fuel control system entered into stoichiometric closed loop fuel control within a manufacturer specified (reasonable) amount of time. The primary determination for entering stoich closed loop control is engine coolant temperature (ECT) and load. Load is monitored via the fuel monitor, thus leaving ECT with a monitoring requirement.
Engine coolant temperature is already modeled to fulfill the thermostat monitoring requirements, however, thermostat regulating temperature is typically 192 deg F while stoich closed loop temperature is typically 50 deg F. This means that the same ECT model can be used, but with different thresholds.
The stoich closed loop ECT threshold is a function of load - a higher ECT value is used at higher loads. The monitor software will pull the ECT value from the calibration table at the minimum load (idle) and use it as the worst case value for the stoich closed loop threshold.
The time to closed loop monitor shares the ECT model with the thermostat monitor. If the modeled ECT reaches the closed loop stoich temperature threshold and actual ECT does not achieve the same temperature (within a tolerance) after a given time interval, a P0125 DTC is set.
Similar to the thermostat test, the test is disabled under conditions where monitoring would be unreliable, e.g., high percentage of time at idle.
Because the thermostat test does not run below 20 deg F, the model accuracy is not understood at those temperatures. For Phase #1 (2015 MY-2016 MY), the time to closed loop monitor will detect faults above 20 deg F, similar to the thermostat monitor. For Phase #2 (2016 MY 2017MY+) a different algorithm is planned for ambients below 20 deg F.
| DTC | P0125 - Insufficient Coolant Temp For Closed Loop Fuel Control |
| Monitor Execution | Once per driving cycle, during a cold start |
| Monitoring Duration | Drive Cycle |
| Entry Conditions | Minimum | Maximum |
| Engine Coolant Temperature at Start | None | 80 °F |
| Intake Air Temperature at start (ambient temp) | 20 °F | None |
| Inferred Percent Ethanol (flex fuel vehicles only) | Learned | N/A |
| Completion Condition | Minimum | Maximum |
| Modeled ECT | 80 °F | None |
| Time Since Modeled ECT Exceeded Threshold | 3 sec. | None |
| Time at Idle/Low Load Compared with Total Engine Run Time | None | 50% |
| Engine Coolant Temperature < 50 °F |