Symptom:
*CMTC DISPLAYS- OC
POSSIBLE CAUSES
AMBIENT TEMP SENSOR GROUND CIRCUIT OPEN
AMBIENT TEMPERATURE SIGNAL CIRCUIT OPEN
CHECKING AMBIENT TEMPERATURE SENSOR
AMBIENT TEMP SENSOR GROUND CIRCUIT OPEN
AMBIENT TEMPERATURE SIGNAL CIRCUIT OPEN
CMTC - AMBIENT TEMPERATURE INCORRECT
TEST
ACTION
APPLICABILITY
1
Turn the ignition off.
Disconnect the ambient temperature sensor harness connector
Note: Check connectors - Clean/repair as necessary.
Remove the ambient temperature sensor.
Measure the resistance of the ambient temperature sensor.
Using the resistance/degrees specifications compare the resistance reading of the
Ambient Temp Sensor, to the air temperature.
SENSOR SPECIFICATIONS: 32°F= 29.3 - 36 Ohms, 50°F= 18 - 22 Ohms, 68°F= 11.4
- 13.6 Ohms, 77°F= 9.1 - 10.8 Ohms, 86°= 7.4 - 8.7 Ohms, 104°= 4.9 - 5,7 Ohms, 122°=
3.3 - 3.8 Ohms
Is the resistance measurement with in the min/max readings, for the current
temperature?
All
Yes
→
Go To
2
No
→
Replace the ambient temperature sensor.
Perform BODY VERIFICATION TEST - VER 1.
Note: After any repair for an ambient temperature sensor problem, the
vehicle must be driven over 3 miles above 25 mph continuouly in order to
update the CMTC display
2
Turn the ignition off, wait 1 minute.
Disconnect the ambient temperature sensor harness connector.
Measure the resistance between ground and the Ambient Sensor Ground circuit.
Is the resistance below 5.0 ohms?
All
Yes
→
Go To
3
No
→
Repair the open in the ambient temperature ground circuit.
Perform BODY VERIFICATION TEST - VER 1.
96
OVERHEAD CONSOLE