Full Test

The Diagnostic Mode also has a self-test function (Full Test) to verify correct instrument cluster operation. When activated, the following occurs:

• The temperature gage and the fuel gage are set to the halfway mark (50%).
• The tachometer is set to 3,000 RPM.
• The speedometer is set to 70 MPH or 70 km/h.
• The chime is activated at 1 kHz.
• The warning indicator LEDs that are driven by either the internal microprocessor or from the serial data line are illuminated. These are Airbag, Brake Park/Fail, Seat Belt and Shift 1 - 4.
• All segments of the MFD and the side LCDs are illuminated.
• Press the MODE button to return to the GM Part Number screen, or the SET button to exit the instrument cluster Diagnostic Mode.

Faults can be identified by using Tech 2 to test instruments and force values and conditions into the instrument cluster. The results of these tests can be used to diagnose problems in the instrument cluster such as faulty gages and switches. Faults within other components can be identified after using Tech 2 to confirm correct operation of the instruments. For example, if there was a reported fault with the speedometer gage and Tech 2 diagnosed the gage as working correctly, then the fault would lie in the powertrain control module (PCM) or in the harness from the speed sensor to the PCM, both of which would then require further testing.