You'll need to set your variance first, then you can calibrate. Here's some info from the manual.
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Setting Variance
(1) Using the Variance Settings map, find your geographic location and note the zone number (Fig. 5).
(2) Turn the ignition switch to the On position. If the compass/thermometer data is not currently being displayed, momentarily depress and release the C/T push button to reach the compass/thermometer display.
(3) Depress the Reset push button and hold the button down until “VARIANCE = XX” appears in the display. This takes about five seconds.
(4) Release the Reset push button. “VARIANCE=XX ” will remain in the display. “XX” equals the current variance zone setting.
(5) Momentarily depress and release the Step push button to step through the zone numbers, until the zone number for your geographic location appears in the display.
(6) Momentarily depress and release the Reset push button to enter the displayed zone number into the CMTC module memory.
(7) Confirm that the correct directions are now indicated by the compass.
Calibrating the Compass
The electronic compass unit features a self-calibrating design, which simplifies the calibration procedure. This feature automatically updates the
compass calibration while the vehicle is being driven. This allows the compass unit to compensate for small changes in the residual magnetism that the vehicle may acquire during normal use. If the compass readings appear to be erratic or out of calibration, perform the following calibration procedure. Also, new service replacement Compass Mini-Trip Computer
(CMTC) modules must have their compass calibrated using this procedure. Do not attempt to calibrate the compass near large metal objects such as other vehicles, large buildings, or bridges; or, near overhead or
underground power lines.
Calibrate the compass manually as follows:
(1) Turn the ignition switch to the On position. If the compass/thermometer data is not currently being displayed, momentarily depress and release the C/T push button to reach the compass/thermometer display.
(2) Depress the Reset push button and hold the button down until “CAL” appears in the display. This takes about ten seconds, and appears about five seconds after “VARIANCE = XX” is displayed.
(3) Release the Reset push button.
(4) Drive the vehicle on a level surface, away from large metal objects and power lines, through three or more complete circles at between five and eight kilometers-per-hour (three and five miles-per-hour) in not less than 48 seconds. The “CAL” message will disappear from the display to indicate that the compass is now calibrated.
NOTE: If the “CAL” message remains in the display, either there is excessive magnetism near the compass, or the unit is faulty. Repeat the calibration procedure one more time.
NOTE: If the wrong direction is still indicated in the compass display, the area selected for calibration may be too close to a strong magnetic field. Repeat the calibration procedure in another location.