2014 Holden Colorado7, Charging system.
Gone are the days of an alternator putting out a regulated voltage that can be easily tested.
The charging system in the current Colorado7 and many other cars is now controlled by the computer network in the vehicle. In this case both Engine Control Module (ECM) and the Body Control Module (BCM) work together to control the alternator.
The Instrument Panel Cluster driver information center is used to notify the driver of system faults.
There are six different “modes’ the charging system can use:
- -Battery Sulfation Mode
- -Charge Mode
- -Fuel Economy Mode
- -Head lamp Mode
- -Start Up Mode
- -Voltage Reduction Mode
The BCM will determine which mode to use based on inputs from the vehicle.
The output voltage is control via a pulse width modulation (PWM) signal from the ECM after the ECM receives a signal from the BCM. Output voltage vs: PWM duty cycle is shown below.
Commanded Duty Cycle – Generator Output Voltage
10% – 11 V
20% – 11.56 V
30% – 12.12 V
40% – 12.68 V
50% – 13.25 V
60% – 13.81 V
70% – 14.37 V
80% – 14.94 V
90% – 15.5 V
One key difference between this system and system used in older cars is that current flow at the battery is monitored by a battery current sensor. The use of the correct battery is critical in the operation of the system. The connection of aftermarket accessories on the WRONG side of the current sensor will cause charging problems. Traditional duel battery systems are also problematic for this style of charging system.
Testing for a charge voltage of 13.5v-14.5v is no longer an indicator of a properly functioning alternator as it is now completely normal for the charge voltage to be outside of this range under normal operation.
The use of a capable Scan Tool and paid subscription to General Motors technical information service is now required for a accurate and efficient testing of the charging system.