Ch 6 page 67
ELECTRICAL SYSTEM
SHOP MANUAL
Adaptation
Fuel injection is optimised through adaptation. In this case the engine control unit adapts to each individual
injector at regular intervals in order to provide the best possible performance and fuel economy.
During adaptation, the engine idles hard with the exhaust brake active.
Alternator
The engine control unit determines when the alternator is to charge. When charging is permitted, i.e. when the
charging conditions are met, the engine control unit sends a signal to the alternator to charge.
The engine control unit receives a signal back from the alternator when it is charging.
If a higher power supply is required, e.g. during cold weather, the engine control unit can request an increase in
alternator charging.
Starter motor
When sending signal from starter switch to the the VCU, the VCU sending canbus signal to the engine
controller The engine control unit activates the starter motor by sending a control voltage to the relay on the
starter motor.
Cooling fan (See in the hydraulic chapter)
The VCU control unit controls the fan speed via a signal to the fan solenoid valve. The VCU receives information
which it then processes to control the fan speed so that the required cooling is obtained.
AC compressor
The VCU unit controls the activation of the AC compressor. When the VCU unit receives a request to activate
the AC compressor, it powers the AC compressor coupling coil.
Exhaust brake (See in the hydraulic chapter)
The VCU is controlling the exhaust brake. When exhaust brake is activated the VCU controls a proportional
solenoid in the hydraulics to distribute pressurized oil to the exhaust brake cylinder.
Interaction with other systems
Functions involving the interaction of the engine control unit with other systems are described below. A more
detailed description is provided under the relevant user function.
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