Toyota 2GR-FE Manual page 332

ES–176
DTC
DESCRIPTION
This DTC is set when the Engine Coolant Temperature (ECT) does not reach 75°C (167°F) despite
sufficient engine warm-up time.
DTC No.
P0128
ES
MONITOR DESCRIPTION
Threshold (75°C
(167°F))
The ECM estimates the ECT based on the starting temperature, engine loads, and engine speeds. The
ECM then compares the estimated temperature with the actual ECT. When the estimated ECT reaches
75°C (167°F), the ECM checks the actual ECT. If the actual ECT is less than 75°C (167°F), the ECM
interprets this as a malfunction in the thermostat or the engine cooling system and sets the DTC.
MONITOR STRATEGY
Related DTCs
Required Sensors/Components (Main)
Required Sensors/Components (Sub)
Frequency of Operation
2GR-FE ENGINE CONTROL SYSTEM – SFI SYSTEM
Coolant Thermostat (Coolant Temperature
P0128
Below Thermostat Regulating Temperature)
DTC Detection Condition
Conditions (a), (b) and (c) are met for 5 seconds (2 rip
detection logic):
(a) Cold start
(b) Engine warmed up
(c) ECT less than 75°C (167°F)
Estimated ECT
ECT
Time
• Thermostat
• Cooling system
• ECT sensor
• ECM
5 seconds
Indicated Coolant Temperature Reading
DTC Set (after 2 Driving Cycles)
P0128: Coolant Thermostat
Thermostat
Engine Coolant Temperature (ECT) sensor, Intake Air Temperature (IAT)
sensor, Vehicle speed sensor
Once per driving cycle
Trouble Area
A082385E20