_GM (U80) - Compass Display

Compass (without Onstar)

The driver information center (DIC) displays the compass based on serial data message from the BCM. The compass module communicates with the body control module (BCM) through a bi-directional data circuit. The instrument panel cluster (IPC) receives compass information from the BCM via the serial data circuit. The compass is displayed in the DIC with other vehicle information and is at the bottom line of the DIC. The compass display shows “- -” when a malfunction is present with the compass module or a compass serial data communication fault exists. The compass displays 'CAL' or 'C' when the compass needs to be calibrated. Cycle the ignition before performing the compass magnetic variation adjustment procedure. Check that the compass module is properly installed in the vehicle since this may cause the compass to malfunction. The embossed arrow on the top of the compass module should be parallel to the centerline of the vehicle.

Compass (with Onstar)

The driver information center (DIC) displays the compass based on serial data message from the Vehicle Communication Interface Module (VCIM). The compass is displayed in the DIC with other vehicle information and is at the bottom line of the DIC. The compass displays 'CAL' or 'C' when the DIC has not received compass information from the VCIM.

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Schematic

The Remote Compass Module (RCM) communicates with the BCM utilizing a single wire Local Interconnect Network (LIN) communication link. The BCM is the gateway for the GMLAN network. All data is communicated on the LIN bus, therefore there are only 3 circuits to the RCM as follows:

• Ground
• LIN bus
• Voltage