P0125

DTC P0125 Insufficient Coolant Temperature For Closed Loop Fuel Control




Circuit Description
To provide the best possible combination of driveability, fuel economy, and emission control, a "Closed Loop" air/fuel metering system is used. When the vehicle is first started, the powertrain control module (PCM) controls fuel delivery in "Open Loop" ignoring the heated oxygen sensor (HO2S) signals and calculating air/fuel ratio based on inputs from the engine coolant temperature, throttle position, and mass air flow sensors.

If the PCM detects that the ECT sensor has not reached a sufficient reading to achieve "Closed Loop" within a specified amount of time, DTC P0125 will set. DTC P0125 is a type B code.

Conditions for Setting the DTC
- No MAP, IAT, ECT, TP, Misfire, Injector, or VSS DTC codes set.

All the above mentioned conditions are true and any combination of the following three tests fail three times in two consecutive ignition cycles (for a total of six failures):

Warm Case Test
- Start-up ECT value is less than 29 °C (84 °F).
- IAT is greater than 10 °C (50 °F).
- Accumulated airflow is greater than 1500 grams.
- Engine run time is greater than 90 seconds.
- Time for coolant to reach stabilized "Closed Loop" value is less than 120 seconds.

Cold Case Test
- IAT is between -7 °C (20 °F) and 10 °C (50 °F)
- Accumulated airflow is greater than 2000 grams.
- Engine run time is less than 225 seconds.
- Time for coolant to reach stabilized "Closed Loop" value is less than 300 seconds.

Other Case Test
- IAT is between -30 °C (-22 °F) and -7 °C (20 °F).
- Accumulated airflow is greater than 3600 grams.
- Engine run time is less than 450 seconds.
- Time for coolant to reach stabilized "Closed Loop" value is less than 600 seconds.

Action Taken When the DTC Sets
- The PCM will illuminate the malfunction indicator lamp (MIL) after the second consecutive trip in which the fault is detected.
- The PCM will store conditions which were present when the Diagnostic Trouble Code was set as Freeze Frame and in the Failure Records data.

Conditions for Clearing the MIL/DTC
- The PCM will turn the MIL OFF on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
- A history Diagnostic Trouble Code P0125 will clear after 40 consecutive warm-up cycles have occurred without a fault.
- Diagnostic Trouble Code P0125 can be cleared by using the Scan Tool's "Clear Info" function.

Diagnostic Aids
DTC P0125 set indicates a faulty ECT sensor. Comparing the engine coolant temperature displayed on a Tech 2 with actual coolant temperature measured with a thermometer may isolate this condition. If the displayed engine coolant temperature is not close to the actual coolant temperature, replace the ECT sensor.

Check for the following conditions:
- Poor connection at PCM - Inspect harness connectors for back-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection.
- Damaged Harness - Inspect the wiring harness for damage; open circuits, shorts to ground, or shorts to voltage. If the harness appears to be OK, observe the display on the Tech 2 while moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the fault.

If DTC P0125 cannot be duplicated, the information included in the Failure Records data can be useful in determining vehicle mileage since the DTC was last set.

Steps 1 - 4:

Steps 5 - 10:

Steps 11 - 12:

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart:
2. Comparing the engine coolant temperature displayed on a Tech 2 with actual coolant temperature measured with a thermometer may isolate this condition. If the displayed engine coolant temperature is not close to the actual coolant temperature, replace the ECT sensor. If the temperatures are closed, the fault is intermittent; refer to Diagnostic Aids.




7. Engine Coolant Temperature