DTC P0125: Closed Loop Temp Not Reached: Testing

Turn the ignition on, with the engine off. With the DRBIII®, read DTCs. Is the Good Trip Counter displayed and equal to zero? If yes, go to next step. If no, go to step 5.

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.

NOTE: Inspect the ECT Sensor terminals and related PCM terminals. Ensure the terminals are free from corrosion and damage. This test works best if performed on a cold engine (cold soak). Extremely cold outside ambient temperatures may cause this DTC to set.

If an ECT DTC is set along with this code, diagnose the ECT DTC first. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . Check cooling system to ensure 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: For this test to be valid, Thermostat must be operating properly. This test works best if performed on a cold soak engine. If engine coolant temperature is more than 180°F (82°C), allow the engine to cool until 150°F (65°C) is reached.

Turn the ignition on, with the engine off. 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 surrounding temperature (ambient temperature). Start the engine. During engine warm-up, monitor the Eng Coolant Tmp Deg value. The value change should be a smooth transition from start-up to normal operating temperature. The value should reach at least 180°F (82°C). Is the Eng Coolant Tmp Deg value increase a smooth transition and does it reach at least 180°F (82°C)? If yes, go to next step. If no, replace the ECT Sensor.

NOTE: This test works best if performed on a cold soak engine. If engine coolant temperature is more than 180°F (82°C), allow the engine to cool until 150°F (65°C) is reached. As the engine warms up to operating temperature, the actual coolant temperature (thermometer reading) and the Eng Coolant Tmp Deg value in the DRBIII® should stay relatively close to each other.

Turn the ignition on, with the engine off. 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. Start the Engine. During engine warm-up, monitor the Eng Coolant Tmp Deg value. The Eng Coolant Temp Deg value change should be a smooth transition from start-up to normal operating temperature. Also, monitor the actual coolant temperature with a thermometer. 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 thermostat.

WARNING: When the engine is operating, DO NOT stand in a direct line with the fan. DO NOT put your hands near the pulleys, belts or fan. DO NOT wear loose clothing.

Conditions that set DTC are not present at this time. The following list may help in identifying the intermittent condition:
- Turn the ignition off. Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or partially broken wires.
- Visually inspect the related wiring harness connectors. Look for broken, bent, pushed out, or corroded terminals.
- Refer to any Technical Service Bulletin (TSB) that may apply.
- With the engine running at normal operating temperature, monitor the DRBIII® Good Trip Counter while wiggling the wiring harness. Look for Good Trip Counter to change to zero.
Were any of the above conditions present? If yes, repair as necessary. If no, test is complete.