Toyota Celica 2005 Repair Manual page 603

DI−404
DTC P0125
CIRCUIT DESCRIPTION
Refer to DTC P0115 on page DI−382.
DTC No.
THW or THA is less than −7°C (19.4°F) at engine start, 20
minutes or more after starting engine, and ECT sensor value is
20°C (68°F) or less (2 trip detection logic)
THW and THA is between −7°C (19.4°F) and 10°C (50°F) at
engine start, 5 minutes or more after starting engine, and ECT
P0125
sensor value is 20°C (68°F) or less (2 trip detection logic)
THW and THA greater than 10°C (50°F) at engine start, 2
minutes or more after starting engine, and ECT sensor value is
30°C (86°F) or less (2 trip detection logic)
MONITOR DESCRIPTION
The ECT (Engine Coolant Temperature) 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 warmed up 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 engine coolant temperature is 0_C (32_F) at engine start. After 5 min. running time, the ECT sensor still
indicates that the engine is not warmed up enough to begin air fuel ratio feedback control of the air−fuel ratio.
The ECM interprets this as a fault in the sensor or cooling system and will set a DTC.
MONITOR STRATEGY
Related DTCs
Required sensors/components
Frequency of operation
Duration
MIL operation
Sequence of operation
2005 CELICA (RM1131U)
DIAGNOSTICS
Insufficient coolant temperature for closed
loop fuel control
DTC Detection Condition
Main sensors/components
Related sensors/components
Continuous
S 2 min. (at engine start, engine coolant or intake air temperature of 10°C (50°F) or more)
S 5 min. (at engine start, engine coolant or intake air temperature of −6.6°C (20°F) to 10°C (50°F))
S 20 min. (at engine start, engine coolant or intake air temperature of less than −6.6°C (20°F))
2 driving cycles
None
− ENGINE (2ZZ−GE)
S Cooling system
S Engine coolant temperature sensor
S Thermostat
P0125
602
Trouble area
Insufficient coolant temperature for closed loop
fuel control
Engine coolant temperature sensor, Cooling sys-
tem, Thermostat
Mass air flow meter
DIC78−02