P0125

3UZ-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0125: Insufficient Coolant Temperature for Closed Loop Fuel Control
P0125 - Insufficient Coolant Temperature for Closed Loop Fuel Control

DESCRIPTION





- A thermistor is built into the Engine Coolant Temperature (ECT) sensor and changes the resistance value according to the engine coolant temperature.

- The structure of the sensor and connection to the ECM are the same as the Intake Air Temperature (IAT) sensor.

HINT
If the ECM detects the DTC P0115, P0117 or P0118, it operates the fail-safe function in which the ECT is assumed to be 80°C (176°F).





HINT
Confirm the ECT using the Techstream. Enter the following menus: Powertrain / Engine / Data List / Coolant Temp.





MONITOR DESCRIPTION

The ECT sensor is used to monitor the temperature of the engine coolant. The resistance of the sensor varies with the actual coolant temperature. The ECM applies a voltage to the sensor and the varying resistance of the sensor causes the signal voltage to vary. The ECM monitors the ECT signal voltage after engine start-up. If, after sufficient time has passed, the sensor still reports that the engine is not warm enough for closed loop fuel control, the ECM interprets this as a fault in the sensor or cooling system and sets a DTC.

Example:

The ECT is 0°C (32°F) at engine start. After about 1 minute of running time, the ECT sensor still indicates that the engine is not warm enough to begin closed-loop fuel (air-fuel ratio feedback) control. The ECM interprets this as a malfunction in the sensor or cooling system and stores the DTC.

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS





TYPICAL MALFUNCTION THRESHOLDS





CONFIRMATION DRIVING PATTERN





- Leave the vehicle outside overnight.

- Connect the Techstream to the DLC3.

- Turn the ignition switch to ON and turn the Techstream on.

- Enter the following menu items: Powertrain / Engine / Data List / Coolant Temp.

- Check that the engine coolant temperature is 10°C (50°F) or less.

- Clear DTCs (even if no DTCs are stored, perform the clear DTC operation).

- Turn the ignition switch off and wait for at least 30 seconds.

- Turn the ignition switch to ON and turn the Techstream on [A].

- Start the engine.

- Wait 21 minutes or more [B].

- Enter the following menus: Powertrain / Engine / Trouble Codes [C].

- Read the pending DTCs.

HINT
- If a pending DTC is output, the system is malfunctioning.
- If a pending DTC is not output, perform the following procedure.
- Enter the following menus: Powertrain / Engine / Utility / All Readiness.

- Input the DTC: P0125.

- Check the DTC judgment result.





- If the test result is INCOMPLETE or UNKNOWN and no pending DTC is output, perform a universal trip and check for permanent DTCs Reading and Clearing Diagnostic Trouble Codes.

HINT
- If a permanent DTC is output, the system is malfunctioning.
- If no permanent DTC is output, the system is normal.
INSEPCTION PROCEDURE

HINT
- If DTCs P0115, P0116, P0117, P0118 and P0125 are output simultaneously, an ECT sensor circuit may be open or shorted. Perform the troubleshooting of DTC P0115, P0117 or P0118 first.
- Read freeze frame data using the Techstream. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.
PROCEDURE

1. CHECK OTHER DTC OUTPUT (IN ADDITION TO DTC P0125)

Result:





HINT
If any other codes besides P0125 are output, perform the troubleshooting for those codes first.

B -- GO TO DTC CHART Diagnostic Trouble Code Descriptions
A -- Continue to next step.

2. INSPECT THERMOSTAT

(a) Check the valve opening temperature of the thermostat.

Standard:

Valve opening temperature is 80 to 84°C (176 to 183°F)

HINT
Also check that the valve is completely closed below the opening temperature shown above.

NG -- REPLACE THERMOSTAT
OK -- Continue to next step.

3. CHECK COOLING SYSTEM

(a) Check for defects in the cooling system that might cause the system to be too cold, such as abnormal radiator fan operation or a modified cooling system.

NG -- REPAIR OR REPLACE COOLING SYSTEM

OK -- REPLACE ENGINE COOLANT TEMPERATURE SENSOR