Chart 1C-9 Incorrect Outside Air Temperature Display
Diagnostic Chart:
Wiring Diagram:
SYSTEM OPERATION
The outside air temperature sensor is a thermistor which changes its resistance as outside air temperature changes. As outside air temperature increases, the sensor resistance decreases. The amount of current allowed to pass through the sensor determines the outside air temperature input as monitored on CKT 735.
OUTSIDE AIR TEMPERATURE DISPLAY UPDATE
To prevent incorrect outside air temperature display due to engine heat, the H-A/C control will allow the outside air temperature display to increase only after one of the following conditions are met:
When Vehicle is First Started
^ Ignition system is turned off for over three hours. The actual outside air temperature will be displayed when the ignition system is turned on.
^ ignition system turned off for less than three hours and engine coolant temperature is less than 10°C (50°F) higher than the outside air temperature reading.
If the above conditions are not met, the outside air temperature display from the previous ignition cycle will be displayed.
When Vehicle is Moving
^ Vehicle speed is between 32 and 72 km/h (20 to 45 mph) for three minutes. If the vehicle speed drops below 32 km/h (20 mph), the timer will reset.
^ Vehicle speed is above 32 km/h (20 mph) for one minute after reaching 72 km/h (45 mph). If the vehicle speed drops below 32 km/h (20 mph), the timer will reset.
The temperature display will be allowed to decrease at any time.
DIAGNOSTIC AIDS
Check for history DTC 101 or 102. While these codes are current, the H-A/C control will use a default value of 9°C (49°F) or 128 A/D counts. There will be no indication that this fault had occurred other than an incorrect outside air temperature display.
Enter diagnostic display mode and display DTCs (if any). Tap on the outside air temperature sensor and wiggle the sensor wiring and electrical connector. If DTC 01 or 02 sets, replace the outside air temperature sensor or repair the electrical connector.