RAM 1500 Truck 4WD V8-5.9L VIN Z (2002)
Compass/Temperature
The CMTC/EVIC simultaneously displays the compass reading and the outside temperature. Outside temperature information is received via the PCI bus
from the FCM. The CMTC or EVIC module internally senses and calculates the compass direction.
Compass Operation
Upon ignition ON, if the calibration information stored in the CMTC/EVIC memory is within the normal range, the CMTC/EVIC will perform in slow
Auto-Cal mode. In slow Auto-Cal mode, the CMTC/EVIC continuously compensates for the slowly changing magnetic field of the vehicle. The compass
module detects changes in the vehicle magnetism and makes appropriate internal corrections to ensure proper displayed direction.
However, if the calibration information stored in the CMTC/EVIC memory is not within the normal range at ignition ON, the CMTC/EVIC will enter
fast Auto-Cal. CAL is displayed along with the temperature.
Auto activation of the fast Auto-Cal mode will also occur when the CMTC/EVIC is subjected to high magnetic field strength levels, which cause all
compass readings to be erroneous for a continuous period of five (5) minutes. During fast Auto-Cal, CAL will be displayed along with the temperature.
Fast Auto-Cal can also be performed manually, by pressing and holding the RESET button for 10 seconds during the Compass/Temperature display
mode.
Ambient Temperature Sensor
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 FCM, 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 FCM. Ambient Temperature Sensor DTC's will be recorded in the FCM. The ATS can be diagnosed using the following
Sensor Test. Test the ATS circuits using the diagnostics in the Body Diagnostic Procedures Manual. If the EVIC passes the self test, and the ATS, the
circuits, and PCI bus communications are confirmed to be OK, but the EVIC temperature display is inoperative or incorrect, replace the FCM.
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.
Compass Calibration
Compass Calibration
The compass module has 2 types of auto-calibration; slow-cal and fast-cal. Slow-cal ensures that during normal vehicle operation the compass performs
auto-calibration functions to keep the compass sensors in their proper operating range. Whenever the ignition is ON and the CMTC/EVIC receives PCI
bus data indicating that engine RPM is greater than zero, auto-calibration is performed continuously.
If the calibration information stored in the compass module memory is not within the normal range after a power-up cycle, the compass will display
CAL. The CMTC/EVIC will enter into the fast-cal mode until calibration is complete.
To enter the compass into Manual Calibration mode, perform the following steps:
