Ambient Temperature Sensor Diagnostics

AMBIENT TEMPERATURE SENSOR
On these equipped vehicles, the Ambient Temperature Sensor is hardwired to the PCM. The ambient air temperature is monitored and displayed by the Compass/Temp Mirror.

The ambient temperature sensor cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.

The resistance in the ambient temperature sensor changes as the outside temperature rises or falls. The PCM senses the change in reference voltage through the ambient temperature sensor resistor. Based on the resistance of the ambient temperature sensor, the PCM is programmed to correspond to a specific temperature. The Compass/Temp Mirror then displays the proper ambient temperature.

Ambient Temperature Sensor Diagnostics
The outside temperature function is supported by the ambient temperature sensor; a signal and ground circuit hardwired to the Compass/Temp Module (1.6L vehicles) or to the PCM (2.0L vehicles), and the Compass/Temp Mirror display.

If the Compass/Temp Mirror display indicates 60 °C (140 °F) or the ambient temperature sensor sense circuit is shorted to ground, the temp display will be 60 °C (140 °F) to indicate a SHORT circuit condition.

If the Compass/Temp Mirror display indicates -45 °C (-49 °F) or the ambient temperature sensor sense circuit is open, the temp display will be -45 °C (-49 °F) to indicate an OPEN circuit condition.

If there is an OPEN or SHORT circuit condition, it must be repaired before the Compass/Temp Mirror VF display can be tested.

The ambient temperature sensor can be diagnosed using the following Sensor Test. If there are no codes stored in the PCM (2.0L vehicles) and the ambient temperature sensor and the circuits are confirmed to be OK, but the temperature display is inoperative or incorrect, replace the Compass/Temp Mirror.

Ambient Temperature Sensor Test
1. Turn the ignition OFF.
2. Disconnect and isolate the battery negative cable.
3. Disconnect the ambient temperature sensor harness connector.
4. Measure the resistance of the ambient temperature sensor using the following values:

TEMPERATURE SENSOR RESISTANCE

0 °C (32 °F) 29.33 - 35.99 Kilohms
10 °C (50 °F) 17.99 - 21.81 Kilohms
20 °C (68 °F) 11.37 - 13.61 Kilohms
25 °C (77 °F) 9.12 - 10.86 Kilohms
30 °C (86 °F) 7.37 - 8.75 Kilohms
40 °C (104 °F) 4.90 - 5.75 Kilohms

The sensor resistance should read between these min/max values. If the resistance value is OK, refer to the Wiring Diagrams to test the Signal and Ground circuits. If the resistance values are not OK, replace the Sensor.