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.
Charging System
The charging system is a negative ground system consisting of the following:
- generator(s)
- internal voltage regulator
- charging system warning indicator
- storage battery
- necessary wiring and cables
The generator(s) are belt-driven by the engine accessory drive system. For additional information, refer to ACCESSORY DRIVE .
The battery is a 12-volt direct current source connected in a negative ground system. The battery case is sealed and includes 2 vent holes to release gases. The battery has 3 major functions:
- engine cranking power source
- voltage stabilizer for the electrical system
- temporary power when electrical loads exceed the generator output current
The single generator system consists of the generator mounted on the top right of the engine (diesel) or top center of the engine (gasoline). The gasoline engine uses a 3G 115-amp generator with a 2.52:1 pulley ratio. The 6.0L diesel engine uses a 6G 110-amp generator with a 2.79:1 pulley ratio.
The dual generator package consists of an upper/lower dual generator system. The 6.0L upper generator is a VR42 140-amp generator with a 2.79:1 pulley ratio. The 6.0L lower generator is a 4G 120-amp generator with a 3.00:1 pulley ratio. The upper and lower generators are not interchangeable.
This system is also monitored and controlled by the PCM. The PCM monitors both the upper and lower generator I circuits to determine the output of both generators and sets possible diagnostic trouble codes (DTCs). The PCM controls the lower generator by turning it off when the glow plug system is commanded on by the PCM to avoid possible damage (excessive voltage) to the glow plugs. As soon as the glow plug system stops cycling, the PCM will supply voltage to the lower generator.
The generators operate independently of the other. Control is through internal voltage regulators. If one generator fails, the other generator can maintain system performance under light load conditions. Under heavy load, the PCM detects a concern, sets a DTC and illuminates the warning indicator.
On the dual generator system, the PCM controls the charging system warning indicator and commands the light on if the PCM detects a concern on the monitored circuits.
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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.