Circuit Operation - Volts Indicator

The Powertrain Control Module (PCM) sends ignition voltage through circuit 225 to the L terminal of the generator. The voltage regulator acknowledges this voltage along with generator rotation. If the generator is not turning (engine off) with the ignition in the RUN position, it will ground the L terminal of the generator. The PCM senses this, and sends a signal over the data line to the instrument cluster. The instrument cluster, in turn lights the VOLTS indicator.

If the generator is turning (engine running), the PCM senses current being produced and commands the VOLTS indicator off.

Whenever the voltage regulator senses a fault condition, it grounds the L terminal of the generator. The PCM senses this and commands the VOLTS indicator on.