Diagnosis and testing

Compass mini-trip computer

If the problem with the compass mini-trip computer module is an "OC" or "SC" in the compass/thermometer display, refer to Ambient Temperature Sensor in the Diagnosis and Testing section of this group. If the problem with the compass mini-trip computer module is an inaccurate or scrambled display, refer to Self-Diagnostic Test in the Diagnosis and Testing section of this group. If the problem with the compass mini-trip computer module is incorrect Vacuum Fluorescent Display (VFD) dimming levels, use a DRB scan tool and the proper Diagnostic Procedures manual to test for the correct dimming message inputs being received from the instrument cluster over the Chrysler Collision Detection (CCD) data bus. If the problem is a no-display condition, use the following procedures. For complete circuit diagrams, refer to Overhead Console in the Contents of Group 8W - Wiring Diagrams.

(1) Check the fused ignition switch output (run/ start) fuse in the junction block. If OK, go to Step 2.

If not OK, repair the shorted circuit or component as required and replace the faulty fuse.

(2) Turn the ignition switch to the On position.

Check for battery voltage at the fused ignition switch output (run/start) fuse in the junction block. If OK, go to Step 3. If not OK, repair the open fused ignition switch output (run/start) circuit to the ignition switch as required.

(3) Turn the ignition switch to the Off position.

Disconnect and isolate the battery negative cable.

Remove the overhead console. Check for continuity between the ground circuit cavities of the roof wire harness connector for the overhead console and a good ground. There should be continuity. If OK, go to Step 4. If not OK, repair the open ground circuit to ground as required.

(4) Connect the battery negative cable. Turn the ignition switch to the On position. Check for battery voltage at the fused ignition switch output (run/start) circuit cavity of the roof wire harness connector for the overhead console. If OK, refer to Self-Diagnostic Test in the Diagnosis and Testing section of this group for further diagnosis of the compass mini-trip computer module and the CCD data bus. If not OK, repair the open fused ignition switch output (run/ start) circuit to the junction block fuse as required.

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:

a. Microprocessor compass circuit test

b. Non-volatile memory read/write test

c. Microprocessor ROM verification test

d. CCD communications test.

(4) Following completion of these tests, the compass mini-trip computer will return to normal operation or display one of two messages: "FAIL" or "CCd." Respond to these test results as follows: a. If no test result message is displayed, but compass mini-trip computer operation is still improper, the use of a DRB scan tool and the proper Diagnostic Procedures manual are required for further diagnosis.

b. If the "FAIL" message is displayed, the compass mini-trip computer module is faulty and must be replaced.

c. If the "CCd" message is displayed, the use of a DRB scan tool and the proper Diagnostic Procedures manual are required for further diagnosis.

d. 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.

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 Compass Demagnetizing in the Service Procedures section of this group.

Ambient temperature sensor

The thermometer function is supported by the ambient temperature sensor, a wiring circuit, and a portion of the compass mini-trip computer module. If any portion of the ambient temperature sensor circuit fails, the compass/thermometer display function will self-diagnose the circuit. An "SC" (short circuit) will appear in the display in place of the temperature, when the sensor is exposed to temperatures above 110 C (230 F), or if the sensor circuit is shorted. An "OC" (open circuit) will appear in the display in place of the temperature, when the sensor is exposed to temperatures below -50 C (-58 F), or if the sensor circuit is open.

The ambient temperature sensor circuit can also be diagnosed using the following Sensor Test, and Sensor Circuit Test. If the temperature sensor and circuit are confirmed to be OK, but the temperature display is inoperative or incorrect, refer to Compass Mini-Trip Computer in the Diagnosis and Testing section of this group. For complete circuit diagrams, refer to Overhead Console in the Contents of Group 8W - Wiring Diagrams.

SENSOR TEST

(1) Turn the ignition switch to the Off position.

Disconnect and isolate the battery negative cable.

Disconnect the ambient temperature sensor wire harness connector.

(2) Measure the resistance of the ambient temperature sensor. At -40 C (-40 F), the sensor resistance is 336 kilohms. At 55 C (131 F), the sensor resistance is 2.488 kilohms. The sensor resistance should read between these two values. If OK, refer to Sensor Circuit Test in the Diagnosis and Testing section of this group. If not OK, replace the faulty ambient temperature sensor.

SENSOR CIRCUIT TEST

(1) Turn the ignition switch to the Off position.

Disconnect and isolate the battery negative cable.

Disconnect the ambient temperature sensor wire harness connector and the overhead console wire harness connector.

(2) Connect a jumper wire between the two terminals in the body half of the ambient temperature sensor wire harness connector.

(3) Check for continuity between the sensor return circuit and the ambient temperature sensor signal circuit cavities of the roof wire harness overhead console connector. There should be continuity. If OK, go to Step 4. If not OK, repair the open sensor return circuit or ambient temperature sensor signal circuit to the ambient temperature sensor as required.

(4) Remove the jumper wire from the body half of the ambient temperature sensor wire harness connector.

Check for continuity between the sensor return circuit cavity of the roof wire harness overhead console connector and a good ground. There should be no continuity. If OK, go to Step 5. If not OK, repair the shorted sensor return circuit as required.

(5) Check for continuity between the ambient temperature sensor signal circuit cavity of the roof wire harness overhead console connector and a good ground. There should be no continuity. If OK, refer to Compass Mini-Trip Computer in the Diagnosis and Testing section of this group. If not OK, repair the shorted ambient temperature sensor signal circuit as required.