RAM 3500 Truck 4WD L6-5.9L DSL Turbo VIN C (2002)
Driver/Vehicle Information Display: Testing and Inspection
Self-Diagnostic Test
CMTC Self-Diagnostic Test
A self-diagnostic test is used to determine that the compass mini-trip computer module is operating properly electrically Initiate the self-diagnostic test as
follows:
1. With the ignition switch in the OFF position, simultaneously depress and hold the Step button and the U.S./Metric button.
2. Turn the ignition switch to the ON position.
3. Continue to hold both buttons depressed until the compass mini-trip computer module enters the display segment test. In this test, all of the
Vacuum Fluorescent Display (VFD) segments are lighted while the compass mini-trip computer module performs the following checks:
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Microprocessor RAM read/write test
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Non-volatile memory read/write test
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Microprocessor ROM verification test
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CCD communications test.
4. Following completion of these tests, the compass mini-trip computer will display one of three messages: "PASS," "FAIL," or "CCD." Respond to
the respective test results as follows:
If the "PASS" message is displayed, but compass mini-trip computer operation is still improper, the use of a DRB scan tool and the proper
Diagnostic Procedures are required for further diagnosis.
If the "FAIL" message is displayed, the compass mini-trip computer module is faulty and must be replaced.
If the "CCD" message is displayed, the use of a DRB scan tool and the proper Diagnostic Procedures are required for further diagnosis.
If any VFD segment should fail to light during the display segment test, the compass mini-trip computer module is faulty and must be replaced.
5. If all tests are passed, or if the ignition switch is turned to the OFF position, the compass mini-trip computer module will automatically return to
normal operation.
NOTE: If the compass functions, but accuracy is suspect, it may be necessary to perform a variation adjustment. This procedure allows the compass
unit to accommodate variations in the earth's magnetic field strength, based on geographic location. Refer to Compass Variation Adjustment in
the Service Procedures section of this group.
If the compass reading has blanked out, and only "CAL" appears in the display, demagnetizing may be necessary to remove excessive residual
magnetic fields from the vehicle. Refer to Compass Demagnetizing in the Service Procedures section of this group.
