ENGINE (J05E)/TROUBLESHOOTING
2–276
DTC: P0128
EN01H02127030602016049
P0128: Thermostat - The coolant temperature does not reach a warmed-up temperature
INFORMATION
1.
Technical description
•
The thermostat prevents coolant from flowing into the radiator when the engine coolant temperature is less than
76.5
C {169.7
F}, in order to secure the engine warm up function. When the temperature rises above 76.5
C
{169.7
F}, the valve opens and allows coolant to flow into the radiator, thereby preventing the engine from over-
heating.
•
If the thermostat fails and the valve stays open, it is difficult for the engine coolant temperature to rise, so the
exhaust components that work after the engine coolant temperature has reached a certain value (warm up) will not
operate for a long time. The thermostat must therefore be diagnosed to see if it is working properly.
<Description of malfunction>
•
In order to detect a malfunction of the thermostat, the above failure is determined when the actual engine coolant
temperature is a certain amount lower than the predicted temperature.
2.
DTC set condition
(1)
DTC detection condition
•
Engine speed
≥
700 r/min
•
Engine coolant temperature at engine start-up
≤
52
C {125.6
F}.
•
Engine coolant temperature is 76
C {168.8
F} or more after running the engine for 60 seconds or more.
(2)
Judgement criteria
•
The condition that the actual engine coolant temperature is less than 65
C {149
F} remains for 5 seconds or
more.
3.
Reset condition
•
After restoration to normal condition.
4.
Indication, warning or system control regulation when the DTC is set.
•
MIL: ON
•
SVS light: OFF
(E)
(THW)
Z5G
X66
ZJQ (E5)
X28 (THW)
10mA
10mA
Engine ECU
Coolant temperature sensor
Body earth
Engine coolant
temperature sensor
Thermostat
Intercooler
Radiator
SHTS021270300255