Engine Control System - SFI System (from 12/2010)

2GR-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, whose resistance value varies according to the engine coolant temperature, is built into the engine coolant temperature sensor.

The structure of the sensor and its connection to the ECM are similar to those of the intake air temperature sensor.





MONITOR DESCRIPTION

The resistance of the ECT sensor varies in proportion to the actual ECT. The ECT supplies a constant voltage to the sensor and monitors the signal output voltage of the sensor. The signal voltage output varies according to the changing resistance of the sensor. After the engine is started, the ECT is monitored through this signal. If the ECT sensor indicates that the engine is not yet warm enough for closed-loop fuel control, despite a specified period of time having elapsed since the engine was started, the ECM interprets this as a malfunction in the sensor or cooling system and sets the DTC.

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS





TYPICAL MALFUNCTION THRESHOLDS





CONFIRMATION DRIVING PATTERN





1. Leave the vehicle outside overnight.

2. Connect the Techstream to the DLC3.

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

4. Enter the following menus: Powertrain / Engine / Data List / All Data / Coolant Temp.

5. Check that the engine coolant temperature is 5°C (41°F) or less.

6. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure) DTC Check / Clear (from 12/2010).

7. Turn the ignition switch off and wait for 30 seconds.

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

9. Start the engine.

10. After starting the engine, wait 21 minutes or more [B].

11. Enter the following menus: Powertrain / Engine / Trouble Codes / Pending.

12. Read the pending DTCs [C].

13. If a pending DTC is output, the system is malfunctioning.

HINT
If a pending DTC is not output, perform the following procedure.

14. Enter the following menus: Powertrain / Engine / Utility / All Readiness.

15. Input the DTC: P0125.

16. Check the DTC judgment result.





HINT
* If the judgment result shows ABNORMAL, the system has a malfunction.
* If the judgment result shows NORMAL, the system is normal.
* If the judgment result shows INCOMPLETE or UNKNOWN, perform step [B] again.

17. Enter the following menus: Powertrain / Engine / Utility / All Readiness.

18. Check the judgment result.

HINT
* If the judgment result shows ABNORMAL, the system has a malfunction.
* If the judgment result shows NORMAL, the system is normal.

19. If the test result is INCOMPLETE or UNKNOWN and no pending DTC is output, perform a universal trip and check for permanent DTCs DTC Check / Clear (from 12/2010).

HINT
* If a permanent DTC is output, the system is malfunctioning.
* If no permanent DTC is output, the system is normal.

WIRING DIAGRAM

Refer to DTC P0115 Engine Control System - SFI System (from 12/2010).

INSPECTION PROCEDURE

HINT
* If any of DTCs P0115, P0116, P0117 or P0118 are set simultaneously with DTC P0125, the Engine Coolant Temperature (ECT) sensor may have an open or a short circuit. Troubleshoot those DTCs first.
* Read freeze frame data using Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction Freeze Frame Data.

PROCEDURE

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

(a) Connect Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine / Trouble Codes.

(e) Read the DTCs.

Result:





HINT
If any DTCs other than P0125 are output, troubleshoot those DTCs first.

B -- GO TO DTC CHART Diagnostic Trouble Code Chart (from 12/2010)
A -- Continue to next step.

2. INSPECT THERMOSTAT

(a) Remove the thermostat Removal.

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

Standard:

80 to 84°C (176 to 183°F)

HINT
In addition to the above check, confirm that the valve is completely closed when the temperature is below the standard.

(c) Reinstall the thermostat Installation.

NG -- REPLACE THERMOSTAT Components
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 any modifications.

NG -- REPAIR OR REPLACE COOLING SYSTEM

OK -- REPLACE ENGINE COOLANT TEMPERATURE SENSOR