GM Service Manual Online
For 1990-2009 cars only

Diagnostic Fault Information

Important: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Circuit/System Description

The inside rear view mirror (ISRVM) uses 2 magnetic field sensors for compass direction. One sensor is for north and south, the other is for east and west. The ISRVM supplies a signal and low reference to each sensor. As the vehicle travels with or against the earths magnetic pull, there will be a change in voltage on one or both sensors. As a result of the change in voltage, the ISRVM changes the heading on the compass display. The internal fault detection for the compass is handled by the inside rear view mirror ISRVM.

Reference Information

Schematic Reference

Instrument Cluster Schematics

Connector End View Reference

Displays and Gages Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Scan Tool Data List

Circuit/System Testing

  1. Ignition ON, compass ON, verify that there is a compass reading on the display.
  2. If the display is blank, replace the ISRVM.
    If the display shows the letter C or CAL, perform the compass calibration procedure. Refer to Compass Calibration and Magnetic Variance .
  3. Verify that the compass reading on the display is correct.
  4. If not correct, perform the compass magnetic variation adjustment procedure. Refer to Compass Calibration and Magnetic Variance .
  5. If the display is still incorrect, replace the ISRVM.

Repair Instructions

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ISRVM replacement, setup, and programming.