2001 C5 On the heads up display every thing shows, but the tachometer. Any ideas on how resolve the issue. Thanks.

 

Did you looked at your Owners Manual on selecting the heads up display items. On my '04, it is page 3-19. Here it what is says:
"The information may be displayed in English or metric
units and appears as an image focused out toward
the front of your vehicle. The HUD consists of the
following information:
• Speedometer
• Turn Signal Indicators
• High-Beam Indicator Symbol
• Tachometer
• Oil, Temperature and Fuel Gages
• Shift Light (Performance SHIFT Light)
This light is used for performance driving to indicate
that the vehicle’s best performance level has been
reached to shift the transmission into the next higher
gear. The SHIFT light will display at an engine speed
of about 5,750 rpm (6,250 rpm on Z06), just prior to
reaching the engine fuel cut-off mode.
• Check Gages Icon
There are five HUD selections that you can choose to
view in the HUD display. By pressing and holding
the PAGE button, you can scroll through these pages
in the following order:
• Speed Only
• Speed and Gage
• Speed, Tachometer and Gage
• Speed and Tachometer
• Tachometer Only
When you have chosen the desired HUD display,
release the PAGE button.
Gages can be scrolled through by tapping the PAGE
button (only when a gage is displayed). The gages
shown are the following:
• Oil Pressure
• Coolant Temperature
• Fuel Level
The selections that you choose will remain in the HUD
display until they are changed."

 

The above is a good place to start. Hopefully it is just a case of the page being set where no Tach displays.

 

Press the mode button until the tach displays.

 

hold down mode