P0641 CHEVROLET - 5 Volt Reference Voltage Incorrect.
If you get reduced power, and those three lights come on at the right side gauge,
you should have codes. That one you listed means the 5V reference signal is
incorrect. That's a short to ground, or short to voltage.
Most of the time, it's going to be your Accelerator Pedal or MAP sensor reference signal.
The pedal interruption will cause low power mode. If you were to unplug your accelerator
pedal harness, put the car in gear, the lower power mode pops up immediately.