Toyota Celica 2005 Repair Manual page 307

DI−108
DTC P0128
CIRCUIT DESCRIPTION
If the engine coolant temperature (ECT) does not reach 75°C (167°F) even if sufficient warm − up time has
elapsed.
DTC No.
Conditions (a), (b) and (c) are met:
(a) After starting engine, ECT is −10 to 30°C (−22 to 86°F)
P0128
(b) Engine is warmed up
(c) THW < 75°C (167°F)
MONITOR DESCRIPTION
Threshold
(75°C(167°F))
The ECM estimates the coolant temperature based on starting temperature, engine loads, and engine
speeds. The ECM then compares the estimated temperature with the actual ECT (Engine Coolant Tempera-
ture). When the estimated coolant temperature reaches 75_C (167_F), the ECM checks the actual ECT. If
the actual ECT is less than 75_C (167_F), the ECM will interpret this as a fault in the thermostat or engine
cooling system and set a DTC.
2005 CELICA (RM1131U)
DIAGNOSTICS
Coolant Thermostat (Coolant Temperature
Below Thermostat Regulating Temperature)
DTC Detecting condition
Estimated ECT
ECT
Time
− ENGINE (1ZZ−FE)
S Thermostat
S Cooling system
S Engine coolant temperature sensor
S ECM
5 sec.
Indicated coolant temp. reading
DTC set (after 2 driving cycles)
306
Trouble Area
DIC6N−02
G00008