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Test E: The Outside Air Temperature Display Does Not Operate Correctly

PINPOINT TEST E: THE OUTSIDE AIR TEMPERATURE DISPLAY DOES NOT OPERATE CORRECTLY

NOTE: The outside air temperature display is only available in base instrument clusters (IC) without electronic automatic temperature control (EATC).

Normal Operation
The outside air temperature sensor is mounted on the radiator core support in front of the radiator and A/C condenser and is hardwired to the instrument cluster (IC) through input circuit VH407 (YE/GN) and return circuit RMC32 (GN/BU). The instrument cluster (IC) provides a reference voltage to the ambient air temperature sensor and monitors the change in voltage resulting from changes in resistance as determined by outside air temperature. When the engine has been off for an extended period of time, or the engine temperature is cold, the instrument cluster (IC) displays the current outside air temperature as measured by the ambient air temperature sensor. When the engine has only been turned off for a short time, or if the engine is not cold, the instrument cluster (IC) takes a reading of the current temperature and compares the current reading against the last reading at key off. If the temperature is less than the last key off temperature reading, the instrument cluster (IC) displays the current temperature. If the temperature is greater than the last key off temperature reading, the instrument cluster (IC) displays the last key off temperature reading until the ambient air temperature has had time to stabilize with vehicle movement.

- DTC B1255 (Air Temperature External Sensor Circuit Open) - is a continuous and on-demand DTC that sets if the instrument cluster (IC) detects an open on the outside air temperature sensor input circuit VH407 (YE/GN). If the instrument cluster (IC) detects an open on the outside air temperature input, the instrument cluster (IC) defaults the display to 23.5°Celsius (75°F).
- DTC B1257 (Air Temperature External Sensor Circuit Short to Ground) - is a continuous and on-demand DTC that sets if the instrument cluster (IC) detects a short to ground on the outside air temperature sensor input circuit VH407 (YE/GN). If the instrument cluster (IC) detects a short to ground on the outside air temperature input, the instrument cluster (IC) defaults the display to 23.5°Celsius (75°F).

This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Ambient air temperature sensor
- Instrument cluster (IC)


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