Dodge Ram 2004, Service Manual

Page: 23 / 642

3.4.1 VEHICLE INFORMATION DISPLAY
The CMTC provides the following functions:
• Compass direction
• Outside temperature
•
Elapsed ignition on time
• Distance to empty
•
Average fuel economy
• Trip Odometer
The CMTC will not display information for any of
the screens for which it did not receive the proper
PCI bus data. Refer to the symptom list in the
Overhead Console section for problems related to
the CMTC.
The CMTC receives the following messages from
the Instrument Cluster:
• Verification of US/Metric status
•
VF display dimming brightness and exterior
lamp status
• Trip Odometer data
The CMTC receives the following message from
the PCM:
•
Vehicle Speed
US/M BUTTON
The US/M button is used to toggle the display
between English and Metric measurement units.
STEP BUTTON
The STEP Button can be used in one of the
following ways:
1. To sequentially select one of 4 displays or blank
display in the following order:
•
Average Fuel Economy
•
Distance to Empty
•
Trip Odometer
• Time Elapsed
• Off (Blank)
2. To set the magnetic variance zone when VARI-
ANCE = X (X = 1 - 15) is indicated in the VF
display.
RESET BUTTON
The RESET Button has two different functions:
1. To clear the trip functions that may be reset
2. To enter and exit the diagnostic mode
Pressing the RESET button once will clear the
trip function that is currently being displayed and
the CMTC will send a PCI bus beep request to the
Instrument Cluster. If the RESET button is pressed
again within 3 seconds, the CMTC will reset ALL of
the trip functions and an additional beep request is
sent to the Instrument Cluster. The trip functions
that may be reset are:
•
Average Fuel Economy
• Trip Odometer
• Elapsed Time
A reset will only occur if one of the trip functions
that may be reset is currently being displayed.
The CMTC module will send a beep request to the
Instrument Cluster.
Simultaneously pressing the RESET button and
the C/T button while turning the ignition from Off
to On will enter the CMTC into the self-diagnostic
mode.
COMPASS/TEMPERATURE (C/T) BUTTON
Actuating the Compass/Temperature Button
(C/T) will cause the CMTC to display the compass
and temperature information. This function will
operate from another traveler display. The CMTC
simultaneously displays the compass reading and
the outside temperature. Outside temperature in-
formation is received via the PCI bus from the
FCM.
The CMTC module internally senses and calcu-
lates the compass direction.
TRAVELER DISPLAY FUNCTIONS
Using the STEP button will change the CMTC
between modes of operation and display the appro-
priate information according to data received from
the PCI Bus.
COMPASS OPERATION
Upon ignition on, if the calibration information
stored in the CMTC memory is within the normal
range, the CMTC will perform in slow Auto-Cal
mode. In slow Auto-Cal mode, the CMTC continu-
ously compensates for the slowly changing mag-
netic 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 memory is not within the normal range
at ignition on, the CMTC 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 is subjected to high
magnetic field strength levels, which cause all com-
pass 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.
SETTING MAGNETIC ZONE VARIANCE
Variance is the difference between magnetic
North and geographic North. For proper compass
function, the correct variance zone must be set.
Refer to the Zone Variance map for the correct zone.
Follow these steps to check or change the variance
zone:
9
GENERAL INFORMATION