The In Car Tenperature Sensor contains a thermistor which measures the temperature of the inside the vehicle. The signal, based on the resistance value, is delivered to the HVAC control unit. This information is used to control the vent output temperature.
DTC B1234 sets if In-Car temperature sensor signal is at or over 4.9V for 0.3 seconds.
Item
Detecting Condition
DTC Strategy
Voltage check
Open in signal circuit
Short to battery in signal circuit
Faulty In-Car temperature sensor
Faulty A/C Control Unit
Enable Conditions
Ignition ON
Threshold value
Sensor signal is at or over 4.9V for 0.3 seconds
Failsafe
Substituded In-Car Temp. = 25? (77?)
? Resistance value of incar temp sensor as a function of temperature.
Temperature(?/?)
Resistance(?)
-20/-4
285.6
20/68
37.4
-10/14
169
30/86
24.1
0/32
97.7
40/104
15.9
10/50
59.67
50/122
10.8