DTC P0125: Closed Loop Temp Not Reached: Testing

Turn ignition on, engine not running. With the DRBIII®, read DTCs. Is the Good Trip counter displayed and equal to zero? If yes, go to next step. If no, turn ignition off and go to step 5.

NOTE: If an ECT DTC set along with this code, diagnose the ECT DTC first. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . Inspect the ECT terminals and related PCM terminals. Ensure the terminals are free from corrosion and damage. The best way to diagnose this DTC is to allow the vehicle to sit overnight outside in order to have a totally cold soaked engine. Extremely cold outside ambient temperatures may have caused this DTC to set.

WARNING: Never open the cooling system when the engine is hot. The system is under pressure. Extreme burns or scalding may result. Allow the engine to cool before opening the cooling system.

Check the cooling system to make sure that the coolant is in good condition and at the proper level. Is the coolant level and condition okay? If yes, go to next step. If no, inspect the vehicle for a coolant leak and add the necessary amount of coolant.

NOTE: This test works best if performed on a cold engine (cold soak).

Turn ignition on, engine not running. With the DRBIII®, read the Eng Coolant Tmp Deg value. If the engine was allowed to sit overnight (cold soak), the temperature value should be a sensible value that is somewhere close to the ambient temperature. If engine coolant temperature is above 180°F (82°C), allow the engine to cool until 150°F (65°C) is reached. Start the Engine. During engine warm-up, monitor the Eng Coolant Tmp Deg value. The temp deg value change should be a smooth transition from start-up to normal operating temp 180°F (82°C). Also monitor the actual coolant temperature with a thermometer. As the engine warms up to operating temperature, the actual coolant temperature (thermometer reading) and the Eng Coolant Tmp Deg in the DRBIII® values should stay relatively close to each other. Thermostat should open at about 195°F (90°C). Did the thermostat open at the proper temperature? If yes, go to next step. If no, replace the thermostat.

NOTE: For this test to be valid, the thermostat must be operating correctly. This test works best if performed on a cold engine (cold soak).

Turn ignition on, engine not running. With the DRBIII® in sensors, read the Eng Coolant Tmp Deg value. If the engine was allowed to sit overnight (cold soak), the temperature value should be a sensible value that is somewhere close to the ambient temperature. If engine coolant temperature is above 180°F (82°C), allow the engine to cool until 150°F (65°C) is reached. Start the engine. During engine warm-up, monitor the Eng Coolant Tmp Deg value. The temp deg value change should be a smooth transition from start-up to normal operating temp 180°F (82°C). The value should reach at least 180°F (82°C). Was the Eng Coolant Tmp Deg value increase a smooth transition and did it reach at least 180°F (82°C)? If yes, test is complete. If no, replace the Engine Coolant Temperature Sensor.

NOTE: Visually inspect the related wire harness. Look for any chafed, pierced, pinched, or partially broken wires. Visually inspect the related wire harness connectors. Look for broken, bent, pushed out, or corroded terminals. Refer to any Technical Service Bulletins (TSB) that may apply.

Perform a wiggle test on the related wire harnesses with the engine running. Watch for the Good Trip counter to change to zero. Were any problems found? If yes, repair wire harness/connectors as necessary. If no, test is complete.