Tachometer stopped working on my 2004 Chevy Impala LS, What is wrong and how do fix the problem?

SOURCE: Both speedometer & tachometer not working, both reading wrong.

"The Fix" works...I would have not believed it untill I did it.... Start the car in reverse and about 5 times later it reset the speedometer back to zero.....wow!

SOURCE: unlock antitheft code for 2004 chevy impala

Radios in the 2004 Impalas are tied to the vehicle's VIN through the computer, so it may be somewhat difficult to get the code. However, the following steps should work:

1. Press and hold the buttons for presets 1 & 4 (may be 2 & 3). The word "SEC" should show.
2. Press the "MIN" button. "000" should be displayed.
3. Press the "MIN" button again to have the second two numbers appear. Record these numbers.
4. Press the "HR" button for the first two numbers to appear. Record these numbers. -- Note: Your number sequence should be the numbers from the "HR" button followed by the numbers from the "MIN" button.
5. Call 1-800-537-5140. This will get you to the GM unlock code automated line. Ignore the prompt and enter "202108#". Next enter your code (remember, HR then MIN) followed by the * key. For example, 1234*. A 3 or 4 digit code will be given to you. If you get a code such as 0532, drop the zero when entering it into your radio.
6. Enter the code into the radio IAW the applicable manual.

SOURCE: my speedometer stop working

It's a bad stepper motor (the device that operates the needle on the gauge).  Replacements can be found on eBay for approx. $4.95 each - just search for "stepper motor".  Just got 6, to replace all of mine.

SOURCE: reset message center window

THIS SHOULD HELP YOU

Turn the ignition to ON without starting the engine. Fully press and release the accelerator pedal three times within five seconds. If the CHG OIL SOON light flashes two times, the system is resetting. Turn the key to OFF, then start the vehicle. If the CHG OIL SOON light comes back on, the system has not reset, repeat the procedure. Follow this procedure to reset the GM Oil Life System using the DE 100 Series Radio®. Turn the ignition to ACC or ON and the radio off. Press and hold the DISP button on the radio for at least five seconds until SETTINGS is displayed. Press the SEEK up or down arrow to scroll through the main menu. Scroll until OIL LIFE appears on the display. Press the PREV or NEXT button to enter the submenu. RESET will be displayed. Press the DISP button to reset. A chime will be heard to verify the new setting and DONE will be displayed for one second. Once the message has been reset, scroll until EXIT appears on the display. Press the DISP button to exit programming. A chime will be heard to verify the exit.

SOURCE: heater does not work on my 2005 chevy impala ls

If you car is coming to temp but you get nothing from the heater the first place to look is the coolant valve for the heater core. It is sometimes called a mixing control. See if the control is jammed or your control cable is frozen or disconnected from this valve.

The valve should be somewhere near the cooling lines leading into the heater core. I am sorry, but they may be under the dashboard as well.

Good luck and be careful.