Test X: The Outside Air Temperature Display Is Inoperative/Inaccurate

PINPOINT TEST X: THE OUTSIDE AIR TEMPERATURE DISPLAY IS INOPERATIVE/INACCURATE

Normal Operation
The outside air temperature sensor is hardwired to the instrument cluster (IC) through input circuit 767 (LB/OG) and return circuit 242 (DG). 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 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 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.

NOTE: On vehicles equipped with electronic automatic temperature control (EATC), the HVAC module displays the outside air temperature. The instrument cluster (IC) only displays the outside air temperature on vehicles that are not equipped with EATC.

- 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 767 (LB/OG). If the instrument cluster (IC) detects an open on the outside air temperature input, the instrument cluster (IC) defaults the display to dashes (------).
- 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 767 (LB/OG). If the instrument cluster (IC) detects a short to ground on the outside air temperature input, the instrument cluster (IC) defaults the display to dashes (------).

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

X1-X2:

X3-X4:

X5-X7: