Repairing CMTC Displays Double Dash (- -) In Temperature Display

Possible Causes:

No response - PCI Bus HVAC.
CMTC Bus message failure.
CMTC.
Ambient Temperature Sensor.
Ambient Temperature Sensor Signal circuit short to Sensor Ground circuit.
Ambient Temperature Sensor Signal circuit short to ground.
Ambient Temperature Sensor Signal circuit open.
Ambient Temperature Sensor Ground circuit open.
A/C-Heater Control Module.

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 .

Testing:

Turn ignition off. Connect DRBIII(R) to DLC. Turn ignition on. Using the DRBIII(R), select SYSTEM MONITORS, then J1850 MODULE SCAN. Does DRBIII(R) display HVAC ON THE BUS? If yes, to next step. If no, see PCI BUS COMMUNICATION FAILURE under COMMUNICATION SYSTEM.

NOTE: Diagnose and repair any HVAC or COMMUNICATION DTCs before proceeding with this test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .

Using the DRBIII(R), select HVAC, MISCELLANEOUS, then ENABLE AMBIENT TEMPERATURE SENSOR. Select BODY, COMPASS MINI-TRIP, SYSTEM TESTS, then AUTO SELF TEST. Does the DRBIII(R) display TEST FAILED: BUS MESSAGE FAILURE? If yes, diagnose any COMMUNICATION DTCs and symptoms. See DIAGNOSTIC TROUBLE CODE DEFINITIONS and SYMPTOM IDENTIFICATION . If no, go to next step.
Using the DRBIII(R), select BODY, COMPASS MINI-TRIP, SYSTEM TESTS, then AUTO SELF TEST. Does the DRBIII(R) display INTERNAL EVIC FAILURE? If yes, replace CMTC. Perform BODY VERIFICATION TEST under VERIFICATION TESTS. If no, go to next step.
Turn ignition off. Disconnect Ambient Temperature Sensor harness connector. 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.
Disconnect A/C-Heater Control Module C1 harness connector. Measure resistance between Ambient Temperature Sensor harness connector terminals No. 1 and 2. Is resistance less than 5 ohms? If yes, repair Ambient Temperature Sensor Signal circuit for short to Sensor Ground circuit. Perform BODY VERIFICATION TEST under VERIFICATION TESTS. If no, go to next step.
Measure resistance between ground and Ambient Temperature Sensor harness connector terminal No. 1. Is resistance less than 5 ohms? If yes, repair Ambient Temperature Sensor Signal circuit for a short to ground. Perform BODY VERIFICATION TEST under VERIFICATION TESTS. If no, go to next step.
Measure resistance between A/C-Heater Control Module C1 harness connector terminal No. 4 and Ambient Temperature Sensor harness connector terminal No. 1. Is resistance less than 5 ohms? If yes, go to next step. If no, repair open in Ambient Temperature Sensor Signal circuit. Perform BODY VERIFICATION TEST under VERIFICATION TESTS.
Reconnect A/C-Heater Control Module C1 harness connector. Disconnect A/C-Heater Control Module C2 harness connector. Measure resistance between A/C-Heater Control Module C2 harness connector terminal No. 4 and Ambient Temperature Sensor harness connector terminal No. 2. Is resistance less than 5 ohms? If yes, replace A/C-Heater Control Module. Perform BODY VERIFICATION TEST under VERIFICATION TESTS. If no, repair open in Sensor Ground circuit. Perform BODY VERIFICATION TEST under VERIFICATION TESTS.