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Home >> Dodge and Ram >> 2003 >> Durango Base, 5.9 Z, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 47 (Message Systems) >> Compass / Mini-Trip Computer >> Diagnosis And Testing-Compass Mini-Trip Computer >> Self-Diagnostic Test

Self-Diagnostic Test

WARNING: This page is about a different car, the 2004 Dodge Dakota and 2003 Dodge Dakota. However, it is still accessible from the selected car via links, so may be relevant.

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:

NOTE: The compass mini-trip computer self-test can also be performed using a DRB III(R). Refer to Auto Self Test under the System Tests.
  1. With the ignition switch in the Off position, simultaneously depress and hold the STEP and RESET buttons while rotating the ignition switch to the Run/On position.
  2. 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:
    • Non-Volatile Memory Status (NVM)
    • RAM Status
    • ROM Status
    • ASIC Communication Test Status
    • Compass Test Status
    • DC Status
    • J1850 Communications Test
    NOTE: If module is equipped with the Universal Transmitter, the module also checks "Universal Transmitter Communication Test Status"
  3. Following completion of these tests, the compass mini-trip computer will display one of two messages: "FAIL" or "PASS." Press RESET or STEP to exit and enter normal mode. Respond to these test results as follows:
    • If no test result message is displayed, but compass mini-trip computer operation is still improper, the use of a DRB III(R) scan tool and the proper Diagnostic Procedures manual 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 "PASS" message is displayed, the compass mini-trip computer module is OK, no faults are present.
    • 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.
  4. If the first seven tests pass, the Compass mini-trip computer shall verify that all the required J1850 messages are present on the J1850 bus. If all required J1850 messages are present on the J1850 bus, or if the ignition switch is turned to the Off position, the compass mini-trip computer module will automatically return to normal operation. The required J1850 messages are:
    • Dimming message
    • Fuel Used message
    • Distance Pulses message
    • Percentage Fuel Tank Full message
    • Fuel Type message
    • VIN (Vehicle Identification Number)
    • Vehicle Speed message
    • Last Engine Off Duration message
    • Ambient Air Temperature message
NOTE: The Fuel Used J1850 message shall be ignored if the engine type is Diesel or Compressed Natural Gas.
NOTE: Pressing the STEP or RESET switches during any portion of the testing procedure will cause the compass mini-trip computer to exit diagnostics and return to compass/temperature mode.
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 STANDARD PROCEDURE-COMPASS VARIATION ADJUSTMENT  .
NOTE: 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 STANDARD PROCEDURE-COMPASS DEMAGNETIZING  .
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