Toyota 2GR-FE Manual page 329

DTC P0125
DESCRIPTION
A thermistor is built into the Engine Coolant Temperature (ECT) sensor, and its resistance value varies
according to the ECT.
The structure of the sensor and its connection to the ECM are the same as those of the Intake Air
Temperature (IAT) sensor.
DTC No.
Engine coolant temperature (ECT) does not reach
P0125 closed-loop enabling temperature for 20 minutes (this
period varies with ECT when engine start)
MONITOR DESCRIPTION
The resistance of the ECT 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.
Example:
The ECT is 0°C (32°F) at engine start. After 5 minutes 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 sets the DTC.
MONITOR STRATEGY
Related DTCs
Required Sensors/Components (Main)
Required Sensors/Components (Related)
Frequency of Operation
Duration
MIL Operation
Sequence of Operation
TYPICAL ENABLING CONDITIONS
Monitor runs whenever following DTCs are not present
MAF sensor circuit fail
IAT sensor circuit fail
ECT sensor circuit fail
Thermostat fail
2GR-FE ENGINE CONTROL SYSTEM – SFI SYSTEM
Insufficient Coolant Temperature for Closed
Loop Fuel Control
DTC Detection Condition
P0125: Insufficient engine coolant temperature for closed-loop fuel control
Thermostat, cooling system
Engine coolant temperature sensor and mass air flow meter
Once per driving cycle
64 seconds: Closed-loop enabling temperature - 8.34°C (15°F) or more
111.2 seconds: Closed-loop enabling temperature - 19.45 to 8.34°C (35 to
15°F)
1,200 seconds: Less than closed-loop enabling temperature - 19.45°C (35°F)
2 driving cycles
None
P0100 - P0103 (MAF sensor)
P0110 - P0113 (IAT sensor)
P0115 - P0118 (ECT sensor)
Not detected
Not detected
Not detected
Not detected
Trouble Area
• Engine coolant temperature sensor
• Cooling system
• Thermostat
ES–173
ES