Engine coolant temperature sensor is located in the engine coolant passage of the cylinder head for detecting the engine coolant temperature.. It contains negative type themistor whoses resistance value is in inverse proportion to temperature. Resistance of watersensor that varies with temperature makes signal voltage of A/C ECU change. In this way A/C ECU detects temperature. Signal of water sensor is used for cold engine lockout control - When the driver operates the heater before the engine is warmed up enough, to prevent driver from unpleasantness of cold air. the heater control unit reduces blower motor speed until coolant temperature reaches the threshold value.
Air conditioner Control Module sets DTC B1202 if Engine coolant temperature sensor has been detected over 4.9V for 0.3sec.
Item
Detecting Condition
Possible cause
DTC Strategy
Voltage check.
Poor connection of connected part.
Open circuit in signal/power harness.
Short circuit in signal/power harness.
Faulty Engine coolant temperature sensor.
Faulty A/C Control Unit.
Enable Conditions
IG KEY ON.
Threshold value
Engine coolant temperature sensor has been detected over 4.9V for 0.3sec.
Failsafe
Control with the value of -2?(28.4?)
Temperature(?/?)
Resistance(?)
-20(-4)
14.13 ~ 16.83
40/104
1.15
0/32
5.79
60/140
0.59
20/68
2.31 ~ 2.59
80/176
0.32