Quiescent Current Control Module
The Quiescent Current Control Module (QCCM) is located in the right side of the luggage compartment adjacent to the Rear Junction Box (RJB), behind the trim panel.
The QCCM in conjunction with the Body Control Module/Gateway Module (BCM/GWM), monitor and control the systems power supply. The Battery Monitoring System (BMS) control module checks the startup battery health by analyzing startup battery quiescent current, current drain or state of charge. The BMS control module determines if any action is required to protect the startup battery. If action is required this is communicated to the BCM/GWM.
The BCM/GWM control logic uses this information to determine if action is required to assist the startup battery protection. The QCCM control software is contained within the BCM/GWM. The QCCM receives open and close command messages from the BCM/GWM via the Local Interconnect Network (LIN) bus and reacts accordingly.
The system comprises 3 components:
- The BMS control module
- The BCM/GWM
- The QCCM.
The QCCM cuts the power supply to other non-essential control modules to avoid excessive discharge of the startup battery. The power supplies are cut by opening the contacts of relays internally within the QCCM. The systems supplied via the QCCM are the infotainment and the climate control systems.
The system will be set in 'Transit mode' on delivery. 'Transit mode' has no QCCM operation and the relays remain closed. Therefore startup battery drain could occur and the system will not react to it. The Pre-Delivery Inspection (PDI) process requires that the system have to be set from 'Transit mode' to 'Normal mode'. This enables the QCCM operation before handing over the vehicle to the customer.
The QCCM has a routine to clean the relay contacts if required. This routine requires using a Jaguar Land Rover (JLR) approved diagnostic equipment and, if unsuccessful, the unit will require replacement.