Toyota Celica 2005, Repair Manual

Page: 304 / 2497

− DIAGNOSTICS ENGINE (1ZZ − FE)
DI − 105
2005 CELICA (RM1131U)
DTC P0125 Insufficient coolant temperature for closed
loop fuel control
CIRCUIT DESCRIPTION
Refer to DTC P0115 on page DI − 87.
DTC No. DTC Detection Condition Trouble Area
P0125
The engine coolant temperature (ECT) is less than − 6.6 ° C
(20
_
F) when starting the engine, and 20 minutes after the en-
gine start, the ECT sensor still indicates below 20 ° C (68 _ F)
S Cooling system
S Engine coolant temperature sensor
S Thermostat
The ECT is between − 6.6 ° C (20 _ F) and 10 ° C (50 _ F) when
start, 5 minutes after the start, the ECT sensor still indicates
below 20
° C (68 _ F)
The ECT is greater than 10 ° C (50 _ F) when starting the engine,
and 2 minutes after the engine start, ECT sensor still indicates
below 20
°
C (68
_
F)
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 P0125
Insufficient coolant temperature for closed loop
fuel control
Required sensors/components
Main sensors/components
Engine coolant temperature sensor, Cooling sys-
tem, Thermostat
Related sensors/components Mass air flow meter
Frequency of operation Continuous
Duration
2 min. (at engine start, engine coolant or intake air temperature of 10 ° C (50 ° F) or more)
5 min. (at engine start, engine coolant or intake air temperature of − 6.6 ° C (20 ° F) to 10 ° C (50 ° F))
20 min. (at engine start, engine coolant or intake air temperature of less than − 6.6 ° C (20 ° F))
MIL operation 2 driving cycles
Sequence of operation None
DIC6M − 02
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