Put back to two connectors from behind the gauges.
With the gauge hanging, turn on the ignition to the ACC position. Wait for 20 seconds and the gauge cluster should calibrate itself.
Speedo and tach setting now is calibrated to be at zero.
Replace the needle, making sure it points to zero. Gently push the needle back on. Note: do not handle the needle by the arm. Hold it at the black plastic center while doing this.
Turn off the ignition. Wait 3 minutes and turn it back to ACC position.
Needle should move as the gauge calibrate itself and then fall back to zero.
If needle does not fall back to zero, carefully remove the needle and repeat this procedure again until needle show zero after calibration.https://www.celicahobby.com/ubbthreads/thread.f_57137_0_collapsed_2__1.html