Incorrect Ambient Temperature Reading Beyond +/- 5 Degrees

Possible Cause:

Ambient Temperature Sensor.
Ambient Temperature Sensor Ground circuit open.
Ambient Temperature Sensor Signal circuit shorted to ground.
Ambient Temperature Sensor Signal circuit open.
CMTC.

CAUTION: Always turn ignition off before disconnecting or connecting any control module connector. Failure to do so could result in damage to control module.

NOTE: Ensure vehicle being tested has a fully charged battery. If it does not, false symptoms may occur.

NOTE: For component location, see appropriate illustration under COMPONENT LOCATIONS . For terminal identification, see appropriate illustration under CONNECTOR IDENTIFICATION . For circuit and wire color identification, see WIRING DIAGRAMS . For component removal and installation procedures, see appropriate component under REMOVAL & INSTALLATION .

NOTE: Ambient temperature display is updated based on time and vehicle speed. At higher speeds, ambient temperature display will be updated more often than at lower speeds. Ambient temperature information is transmitted to the CMTC on the PCI Bus.

NOTE: Ensure CMTC is communicating on PCI Bus. If CMTC is not communicating on the PCI Bus, see PCI BUS COMMUNICATION FAILURE under COMMUNICATION SYSTEM.

Testing:

Turn ignition off. Disconnect Ambient Temperature Sensor harness connector. Ensure CMTC temperature display is in the desired mode of either Celsius (C°) or Fahrenheit (F°). Measure resistance across Ambient Temperature Sensor terminals (component side). Compare results with AMBIENT TEMPERATURE SENSOR RESISTANCE table. Is resistance as specified? If yes, go to next step. If no, replace Ambient Temperature Sensor. Perform BODY VERIFICATION TEST under VERIFICATION TESTS.

AMBIENT TEMPERATURE SENSOR RESISTANCE

Ambient Temperature - °F (°C)	Ohms
32 (0)	29,330-35,990
50 (10)	17,990-21,810
68 (20)	11,370-13,610
77 (25)	9120-10,880
86 (30)	7370-8750
104 (40)	4900-5750
122 (50)	3330-3880

Measure resistance between ground and Ambient Temperature Sensor harness connector terminal No. 2. Is resistance less than 5 ohms? If yes, go to next step. If no, repair open in Sensor Ground circuit. Perform BODY VERIFICATION TEST under VERIFICATION TESTS.
Measure resistance between ground and Ambient Temperature Sensor harness connector terminal No. 1. Is resistance less than 5 ohms? If yes, repair open in Ambient Temperature Sensor Signal circuit. Perform BODY VERIFICATION TEST under VERIFICATION TESTS. If no, go to next step.
Disconnect A/C-Heater Control Module C1 harness connector. Measure resistance between Ambient Temperature Sensor harness connector terminal No. 1 and A/C-Heater Control Module C1 harness connector terminal No. 4. Is resistance less than 5 ohms? If yes, replace CMTC. Perform BODY VERIFICATION TEST under VERIFICATION TESTS. If no, repair open in Ambient Temperature Sensor Signal circuit. Perform BODY VERIFICATION TEST under VERIFICATION TESTS.