Compass/Temperature Module (CTM)

COMPASS/TEMPERATURE MODULE (CTM)
The overhead console houses the Compass/Temperature Module display and two reading and courtesy lamps. This display provides the outside temperature and one of eight compass readings to indicate the direction the vehicle is facing. The ambient temperature sensor (ATS) monitors outside temperature and is hardwired to the Compass/Temperature Module.

There is a STEP button for the compass/temperature display located forward of the power sunroof switch (if equipped), between the lamps.

The STEP button is used to toggle the compass/temperature display to select either F degrees, C degrees, or OFF. When the vehicle is first turned ON, you may select:
- Blank display
- Compass/Temperature displayed in Fahrenheit (F degrees)
- Compass/Temperature displayed in Celsius (C degrees)

Depress and release the STEP button to cycle through the above display modes.







Setting Magnetic Zone Variance
Variance is the difference between magnetic North and geographic North. For proper compass function, the correct variance zone must be set. Refer to the Zone Variance map for the correct zone.

Follow these steps to check or change the variance zone:
- The ignition switch must be in the ON position and the Compass/Temperature Module display must not be blank.
- Depress and hold the STEP button for 5 - 10 seconds until ZONE appears in the display, then release the STEP button. The number displayed is the variance zone currently stored in the compass memory.
- To change the zone, depress the STEP button to scroll through the zone numbers 1 through 15, until the desired zone is displayed.
- After selecting the zone, wait approximately 15 seconds until the display returns to normal.



Compass Calibration

NOTE: Upon installation of a new overhead console, with the ignition ON, "CAL" will be illuminated in the display but the compass will not calibrate for 30 ignition cycles or 15 starts, OR until manually calibrated. For this reason, manual calibration of the compass is recommended after any replacement or appearance of the compass/temp display being "locked-up."




Manual Calibration
After any replacement or the appearance of a "locked-up" condition, you must calibrate the compass. Follow these instructions in order to ensure correct compass calibration:
- Drive the vehicle to an area away from any large metal objects or overhead power lines.
- Ensure that the proper variance zone is selected. See "Setting Magnetic Zone Variance."
- With the engine running, depress and hold the STEP button for 10 - 15 seconds.
- ZONE will appear in display, then CAL.
- Release the STEP button within 2 seconds of CAL illuminating.
- CAL is displayed.
- Drive slowly, less than 5 MPH (8 KPH) in 3 complete 360 degree circles.
- CAL will stay illuminated to alert the driver that the Compass/Temperature Module is in the calibration mode.
- After calibration, the CAL will turn off.



Auto Calibration Mode
During normal vehicle operation, the Compass/Temperature Module will continuously update the compass calibration to compensate for changes in the vehicle's magnetic field. If the Compass/Temperature Module appears to be "locked-up" or the compass displays false indications, the vehicle may need to be demagnetized. Refer to Demagnetizing Procedure.




Outside Temperature

NOTE: Engine temperature or the vehicle experiencing a "hot soak" condition can increase the temperature near the ambient temperature sensor. The displayed temperature may appear to update slowly until the vehicle is driven and the compass performs directional updates.

The displayed outside temperature information is stored within the compass/temp module. When the Compass/Temperature Module is first powered up, it retrieves the temperature data from the module memory. The memory temperature is compared with the temperature received from the ambient temperature sensor (ATS). The colder of the two temperatures is displayed.


Temperature Update - Warm
On power up, when the outside temperature sensed by the ATS is warmer than the temperature stored in the module memory, the Compass/Temperature Module will update the displayed temperature to the outside air temperature within 30 seconds after it has detected that the vehicle has been moving for 2 minutes.

Temperature Update - Cold
On power up, when the outside air temperature sensed by the ATS is colder than the stored memory temperature, the Compass/Temperature Module will update the displayed temperature to the outside temperature at a rate of -1 degrees F every 2 seconds, regardless if the vehicle is moving or not.

Extreme Temperature / Open or Short Circuit Condition
If the measured outside temperature is more than 60 degrees C (140 degrees F) or the ATS sense circuit is shorted to ground, the temp display will be 60 degrees C (140 degrees F) to indicate a short circuit condition.

If the measured outside temperature is less than -45 degrees C (-49 degrees F) or the ATS sense circuit is open, the temp display will be -45 degrees C (49 degrees F) to indicate an open circuit condition.




Ambient Temperature Sensor
The ambient air temperature is monitored and displayed by the compass/temp module. The Compass/Temperature Module receives a hardwire input from the ambient temperature sensor (ATS). The ATS is mounted on the center support brace in front of the A/C condenser, behind the front grille.

The ATS cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.

The ATS is a variable resistor that operates on a 5-volt reference signal circuit hardwired from the Compass/Temperature Module. The resistance in the ATS changes as the outside temperature rises or falls. The Compass/Temperature Module senses the change in reference voltage through the ATS resistor. Based on the resistance of the ATS, the Compass/temperature Module is programmed to correspond to a specific temperature The Compass/Temperature Module then displays the proper ambient temperature.



Diagnosis And Testing

Self-Check Diagnostics
1. With the ignition switch in the OFF position, depress and hold the STEP button.
2. Turn the ignition switch to the ON position and release the STEP button.
3. All of the VFD segments will illuminate for 2 - 4 seconds. Check for segments that do not illuminate or illuminate all the time.
4. The self-check is complete when an F (FAIL), or a P (PASS) is displayed. If an F is displayed, the overhead console must be replaced. The CTM will not display an F for a VF segment that does not illuminate.
5. To exit the self-check mode, depress the STEP button or cycle the ignition switch and the Compass/Temperature Module will return to normal operation.



Ambient Temperature Sensor
The outside temperature function is supported by the ambient temperature sensor (ATS), a signal and ground circuit hardwired to the compass/temp module, and the display.

If the display indicates 60 degrees C (140 degrees F) or the ATS sense circuit is shorted to ground, the temp display will be 60 degrees C (140 degrees F) to indicate a SHORT circuit condition.

If the display indicates -45 degrees C (-49 degrees F) or the ATS sense circuit is open, the temp display will be -45 degrees C (-49 degrees F) to indicate an OPEN circuit condition.

If there is an OPEN or SHORT circuit condition, it must be repaired before the VF display can be tested.

The ATS can be diagnosed using the following Sensor Test. Test the ATS circuits using the diagnostics in the Body Diagnostic Procedures. If the ATS and the circuits are confirmed to be OK, but the temperature display is inoperative or incorrect, replace the Compass/Temperature Module.

Ambient Temperature Sensor Test
1. Turn the ignition OFF.
2. Disconnect and isolate the battery negative cable.
3. Disconnect the ATS harness connector.
4. Measure the resistance of the ATS using the following min/max values:

0 degrees C (32 degrees F) Sensor Resistance = 29.33 - 35.99 Kilohms
10 degrees C (50 degrees F) Sensor Resistance = 17.99 - 21.81 Kilohms
20 degrees C (68 degrees F) Sensor Resistance = 11.37 - 13.61 Kilohms
25 degrees C (77 degrees F) Sensor Resistance = 9.12 - 10.86 Kilohms
30 degrees C (86 degrees F) Sensor Resistance = 7.37 - 8.75 Kilohms
40 degrees C (104 degrees F) Sensor Resistance = 4.90 - 5.75 Kilohms


The sensor resistance should read between these min/max values. If the resistance values are not OK, replace the Sensor.