Jeep Cherokee 2000 Service Manual - page 563
a. In the display segment test, if any segment
should fail to light the unit is faulty and must be
replaced.
b. If the internal circuitry test is failed, the mod-
ule will display “FAIL”. If “FAIL” is displayed, the
unit is faulty and must be replaced.
c. If the CCD data bus message test is failed, the
module will display “CCD”. If “CCD” is displayed, the
use of a DRB scan tool and the proper Diagnostic
Procedures manual are required for further diagno-
sis.
(5) Momentarily depress and release either button
one time to exit the self-diagnostic test mode and
return the trip computer, compass, and thermometer
display module 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 mag-
netic field strength, based on geographic location.
See the Compass Variation Adjustment procedures,
in this group.
NOTE: If the compass reading has blanked out, and
only “CAL” appears in the display module, demag-
netizing may be necessary to remove excessive
residual magnetic fields from the vehicle. See the
Compass Demagnetizing procedure, in this group.
THERMOMETER
The thermometer function is supported by a ambi-
ent temperature sensor, a wiring circuit, and a por-
tion of the overhead console trip computer, compass,
and thermometer display module display. The sensor
is mounted outside the passenger compartment near
the front and center of the vehicle.
If any portion of the ambient temperature sensor
circuit fails, the thermometer display will self-diag-
nose the circuit. An “SC” (short circuit) will appear in
the display in place of the temperature, when the
sensor is exposed to temperatures above 55° C (131°
F), or if the sensor circuit is shorted. An “OC” (open
circuit) will appear in the display in place of the tem-
perature, when the sensor is exposed to temperatures
below -40° C (-40° F), or if the sensor circuit is open.
The ambient temperature sensor circuit can also be
diagnosed using the following Sensor Test, and Sen-
sor Circuit Test. If the temperature sensor and cir-
cuit are confirmed to be OK, but the temperature
display is inoperative or incorrect, see the Trip Com-
puter, Compass, and Thermometer Display Module
diagnosis in this group. For circuit descriptions and
diagrams, refer to 8W-49 - Overhead Console in
Group 8W - Wiring Diagrams.
SENSOR TEST
(1) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Unplug the temperature sensor wire harness connec-
tor.
(2) Measure the resistance of the temperature sen-
sor. At -40° C (-40° F), the sensor resistance is 336
kilohms. At 55° C (131° F), the sensor resistance is
2.986 kilohms. The sensor resistance should read
between these two values. If OK, go to the Sensor
Circuit Test. If not OK, replace the faulty sensor.
SENSOR CIRCUIT TEST
(1) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Unplug the ambient temperature sensor wire har-
ness connector and the overhead console wire har-
ness connector.
(2) Connect a jumper wire between the two termi-
nals in the body half of the sensor wire harness con-
nector.
(3) Check for continuity between the sensor return
circuit and the ambient temperature sensor signal
circuit cavities of the overhead console wire harness
connector. There should be continuity. If OK, go to
Step 4. If not OK, repair the open circuit as required.
(4) Remove the jumper wire from the ambient tem-
perature sensor wire harness connector. Check for
continuity between the sensor return circuit cavity of
the overhead console wire harness connector and a
good ground. There should be no continuity. If OK, go
to Step 5. If not OK, repair the short circuit as
required.
(5) Check for continuity between the ambient tem-
perature sensor signal circuit cavity of the overhead
console wire harness connector and a good ground.
There should be no continuity. If OK, see the Trip
Computer, Compass, and Thermometer Display Mod-
ule diagnosis in this group. If not OK, repair the
short circuit as required.
SERVICE PROCEDURES
COMPASS VARIATION ADJUSTMENT
Variance is the difference between magnetic north
and geographic north. In some geographic locations,
the difference between magnetic and geographic
north is great enough to cause the compass to give
false readings. If this problem occurs, the compass
variance must be set.
To set the compass variance:
(1) Using the Variance Settings map, find your
geographic location and note the zone number (Fig.
1).
8V - 4
OVERHEAD CONSOLE SYSTEMS
XJ
DIAGNOSIS AND TESTING (Continued)