P0125

2GR-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0125: Insufficient Coolant Temperature for Closed Loop Fuel Control

DTC P0125 - Insufficient Coolant Temperature for Closed Loop Fuel Control

DESCRIPTION

A thermistor is built into the engine coolant temperature sensor, of which the resistance value varies according to the engine coolant temperature.
The structure of the sensor and its connection to the ECM are the same as those of the intake air temperature sensor.

HINT: When any of these DTCs are set, check the engine coolant temperature by selecting the following menu items: Powertrain / Engine and ECT / Data List / All Data / Coolant Temp.










MONITOR DESCRIPTION

The resistance of the engine coolant temperature sensor varies in proportion to the actual engine coolant temperature. The ECM 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 engine coolant temperature is monitored through this signal. If the engine coolant temperature 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.

Example:
The engine coolant temperature is 0°C (32°F) at engine start. After 5 minutes running time, the engine coolant temperature 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 sets the DTC.

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS





TYPICAL MALFUNCTION THRESHOLDS





WIRING DIAGRAM





INSPECTION PROCEDURE
HINT:
- If any of DTCs P0115, P0116, P0117 or P0118 are set simultaneously with DTC P0125, the engine coolant temperature sensor may have an open or a short circuit. Troubleshoot those DTCs first.
- Read freeze frame data using the 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.

PROCEDURE

1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0125)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch on (IG).
(c) Turn the tester on.
(d) Select the following menu items: Powertrain / Engine and ECT / Trouble Code.
(e) Read the DTCs.
Result:





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

B -- GO TO DTC CHART
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
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