Ambient Temperature Sensor

The ambient air temperature is monitored by the PCM and displayed by the CMTC/EVIC. The PCM receives a hardwire input from the ambient temperature sensor (ATS).

The ATS is a variable resistor that operates on a 5-volt reference signal circuit hardwired from the PCM. The resistance in the ATS changes as the outside temperature rises or falls. The BCM senses the change in reference voltage through the ATS resistor. Based on the resistance of the ATS, the PCM is programmed to correspond to a specific temperature. The PCM stores and filters the ambient temperature data and transmits this data to the CMTC/EVIC via the PCI Bus. The ATS cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.

AMBIENT TEMPERATURE SENSOR FAULT CODES 

The outside temperature function is supported by the ambient temperature sensor (ATS), a signal and ground circuit hardwired to the PCM, and the CMTC/EVIC display.

If the CMTC/EVIC display indicates 54°C (130°F) or the ATS sense circuit is shorted to ground, the temp display will be 54°C (130°F) to indicate a SHORT circuit condition.

If the CMTC/EVIC display indicates -40°C (-40°F) or the ATS sense circuit is open, the temp display will be -40°C (-40°F) to indicate an OPEN circuit condition.

If there is an OPEN or SHORT circuit condition, it must be repaired before the CMTC/EVIC VFD can be tested.

The ATS is supported by the PCM. Ambient Temperature Sensor DTCs will be recorded in the PCM. The ATS can be diagnosed using the following Sensor Test. Test the ATS circuits using the diagnostics in SELF-DIAGNOSTICS . If the CMTC/EVIC passes the self test, and the ATS, the circuits, and PCI bus communications are confirmed to be OK, but the CMTC/EVIC temperature display is inoperative or incorrect, replace the PCM.

AMBIENT TEMPERATURE SENSOR TEST 

1. Turn the ignition OFF.
2. Disconnect the ATS harness connector.
3. Measure the resistance of the ATS using the following min/max values:

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

The sensor resistance should read between these min/max values. If the resistance values are not OK, replace the Sensor.