Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Circuit Description
PCM uses generator field duty cycle signal circuit to monitor duty cycle of generator. generator field duty cycle signal circuit connects to high side of field winding in generator. A Pulse-Width Modulated (PWM) high side driver in voltage regulator turns field winding ON and OFF. PCM uses PWM signal input to determine generator load on engine. This allows PCM to adjust idle speed to compensate for high electrical loads. PCM monitors state of generator field duty cycle signal circuit. When key is in RUN position and engine is OFF, PCM should detect a duty cycle near zero percent. However, when engine is running, duty cycle should be between 5 percent and 100 percent. PCM monitors PWM signal using a key ON test and a RUN test. During tests, if PCM detects an out of range PWM signal, DTC P0622 will set. When DTC sets, PCM will send a class 2 serial data message to IPC to illuminate charge indicator.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.