ELECTRONIC COMPASS CALIBRATION PROCEDURE

VEHICLES AFFECTED: 1988 - 1989 "H" AND "W" MODELS

This bulletin has been revised to include 1989 model year and additional information on compass calibration procedures on 'W' Model.

For 1988 and 1989 the above models will be equipped with an electronic compass. This compass will be standard on the 'H' model and optional on the 'W' model.

During pre-delivery, it may be necessary to calibrate the compass. If this situation arises, follow the listed procedures:

1988-89 'H' Models

If the display does not move off true north, and/or the word "CALIBRATE" appears, calibrate as denoted below:

1. Select an open area away from power lines and large steel framed structures. A large level parking lot that you can safely drive the vehicle in a complete circle is recommended.

2. Depress the mode button and hold depressed until the word calibrate appears in the upper left corner of the display. The word "CALIBRATE" should be flashing, indicating that it is waiting for the calibration process to begin.

3. Check to be sure traffic is clear and begin driving the vehicle in a circle. Keep speed below 8 kph (5 mph). When the word "CALIBRATION" stops flashing, the operation is complete.

4. If the compass does not calibrate in three circles or less, it is possible some magnetic disturbance is present. Choose a different location and repeat the process beginning with step 2. Check to be sure that there are no strong magnetic devices, such as a magnetic base mount CB antenna, on the trunk lid or near the rear window. The compass sensor is located under the back window and will be affected by such devices.

5. With the car running or parked with the ignition on, depress the mode button and hold it down until the word "ZONE" appears in the upper right corner of the display.

6. Refer to Figure 1 (Zone Map) for the correct zone to enter according to your present location. If the zone display does not indicate the correct zone, change it by depressing the "SET" button until the correct zone appears. There are a total of 16 zones (00 through 15) but only 9 within North America.

7. When the correct zone appears, depress the "MODE" button again to enter the zone into the compass memory. This completes the calibration procedure.

CALIBRATION PROCDEURE FOR 1988-89 'W' Model ------------------------------------------- The compass in the 'W' Model may be thrown out of calibration by a number of conditions. These include close proximity to a strong magnetic force other than the earths' magnetic field, disconnecting the battery, or heavy current draw caused by excessive use of electrical equipment. When this occurs, the message "CALIBRATE COMPASS" will scroll across the display 3 times a minute.

IMPORTANT: The following procedures must be completed within 60 seconds or the procedure will have to be repeated.

1. Locate an open, level parking lot or field.

2. Depress the "CALIBRATION" button on the compass. Display will read "CAL-IB."

3. Drive the vehicle in a circle clockwise. The circle should be as small as possible. The vehicle speed should be 12 kph (10 mph) or less. It is recommended that all lights (inside and out) be off during calibration: and refrain from using the brakes, which would activate the brake lights.

4. The message "CAL-SET" appears briefly for 1-2 seconds upon completion of the calibration.

5. Point the vehicle toward true north as determined by a road map or hand held compass (if using a hand held compass, take a reading about 20 feet away from the vehicle before beginning the calibration process. This will reduce the chances of magnetic interference). wait one second after stopping.

6. Depress the "NORTH" button, then the message "N-SET" will appear briefly upon completion of calibration.

Several conditions may create a directional error, or make recalibration necessary:

- A local magnetic field deviation causes a directional error.

- A bridge, tunnel, a truck load of metal cargo, or electric railway crossings may interfere with the compass momentarily.

- A magnet or an add-on antenna causes a directional error.

- Cellular phones may cause the compass to lose calibration.

- Recalibration may be required if the vehicle experiences a hard shock to its exterior.

- Recalibration will be necessary after every battery disconnection.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.