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Home >> Jeep >> 2025 >> Grand Cherokee Altitude, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 78 (2.0L - DTCS P0108 To P0125) >> DTC Troubleshooting >> P0125 Insufficient Coolant Temp For Closed-Loop Fuel Control >> Theory Of Operation

Theory Of Operation

WARNING: This page is about a different car, the 2025 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

The Engine Coolant Temperature (ECT) Sensor rationality diagnostic looks at the outputs of three temperature sensors and compares them under cold start conditions. Following a start to run delay time the outputs of the Ambient Air Temperature (AAT) Sensor, Engine Coolant Temperature (ECT) Sensor, and Intake Air Temperature (IAT) Sensor will be compared. If the IAT and AAT Sensors agree and the coolant temperature does not agree, the ECT Sensor is declared as irrational. If declared irrational a second comparison will be done after a short drive cycle.