Download 1. Disconnect the alternator and the Powertrain Control Module (PCM). Check the Violet (VT) (GENerator MONitor or GENMON) wire from the alternator to pin 20 of the PCM connector and the Red/Pink (RD/PK) (GENerator COMmand or GENCOM) wire from the alternator to pin 45 of the PCM for high resistance, an open, or a short to ground. Repair the wiring as needed. 2. If the wiring checks OK, reconnect the PCM and alternator. Start the engine and monitor the VT wire for a roughly 0-10v square wave signal. The signal will be around 40-50% normally with no loads on the system and minimal charging system output. As the load increases, the duty cycle should increase (NOTE: the duty cycle is a positive duty cycle so as the duty cycle increases, the voltage high time increases).