Trip Computer: Testing and Inspection

TEMPERATURE
The Compass Mini-Trip Computer (CMTC) receives Programmable Communications Interface bus (PCI bus) messages from the Body Control Module for all displayed information except the compass display If a dash (-) is displayed, the Compass Mini-Trip Computer is not receiving a PCI bus message from the BCM. To check out the PCI bus line and the BCM use the DRB III scan tool and proper Body Diagnostic Procedure.

If Compass Mini-Trip Computer displays a temperature reading more than 54 °C (130 °F). Check for a short circuit between the temperature sensor and the BCM.

If Compass Mini-Trip Computer displays a temperature reading less than -40 °C (67 °F). Check for an open circuit between the temperature sensor and the BCM.

AVERAGE FUEL ECONOMY
Compass Mini-Trip Computer receives average fuel economy information from the BCM over the PCI bus line. If Compass Mini-Trip Computer displays -. - instead of an average fuel economy value, it is not receiving a PCI bus message for the average fuel economy from the BCM. To check out the PCI bus line and the BCM use the DRB III scan tool.

DISTANCE TO EMPTY
Compass Mini-Trip Computer receives distance to empty information from the BCM over the PCI bus line. If Compass Mini-Trip Computer displays a dash (-) instead of a distance to empty value, it is not receiving a PCI bus message for the distance to empty from the BCM. To check out the PCI bus line and the BCM use the DRB III scan tool.

INSTANTANEOUS FUEL ECONOMY
Compass Mini-Trip Computer receives instantaneous fuel economy information from the BCM over the PCI bus line. If Compass Mini-Trip Computer displays a dash (-) instead of an instantaneous fuel economy value, it is not receiving a PCI bus message for the instantaneous fuel economy from the BCM. To check out the PCI bus line and the BCM use the DRB III scan tool.

TRIP ODOMETER
Compass Mini-Trip Computer receives trip odometer information from the Cluster over the PCI bus line. If Compass Mini-Trip Computer displays dashes instead of the trip odometer value, it is not receiving a PCI bus message for the trip odometer from the Cluster. To check out the PCI bus line and the BCM, use the DRB III scan tool.

ELAPSED TIME
Compass Mini-Trip Computer receives a PCI bus message containing elapsed time information. If Compass Mini-Trip Computer displays dashes -: -- instead of the elapsed time, it is not receiving a PCI bus message for the elapsed time from the BCM. To check out the PCI bus line and the BCM, use the DRB III scan tool.

COMPASS DISPLAY
To display the vehicle direction, the Compass Mini-Trip Computer processes information from a sensor internal to the module. The Compass Mini-Trip Computer is self-calibrating and requires only variance adjustments dependent upon location. The Compass Mini-Trip Computer displays the label CAL whenever the compass is in the fast calibration mode.

If all three of the following conditions listed below occur, the vehicle must be demagnetized.
- Compass portion of the display is blank
- Temperature portion of the display is OK
- The label CAL is illuminated

If demagnetizing the vehicle is needed, refer to the demagnetizing procedure in this section. After demagnetizing, to calibrate the compass refer to Calibration Procedure and to set the variance refer to Variance Procedure, both within this section. If the compass portion of the display is still blank, replace the Compass Mini-Trip Computer.

COMPASS MINI-TRIP COMPUTER - SELF DIAGNOSTIC TEST
1. With the ignition switch in the OFF position simultaneously press the C/T and STEP buttons and hold.
2. Turn ignition switch ON, then release C/T and STEP buttons.
3. Compass Mini-Trip Computer lights all segments on the VFD for 2-4 seconds. Check for segments that are not illuminated.
4. If Compass Mini-Trip Computer displays PASS, the module is OK.
5. If Compass Mini-Trip Computer displays FAIL, replace the module.
6. If Compass Mini-Trip Computer displays bUS, check for an open or a short in the PCI bus communication circuit.
7. Press the C/T or the STEP button to exit self-test.