Battery And Cables - Project 8: Overview: Notes

WARNING: This page is about a different car, the 2020 Jaguar XE and 2019 Jaguar XE. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION: When connecting a slave power supply to the vehicle, to avoid damaging the Battery Monitoring System (BMS) control module, always use the jump start ground terminal stud point. The jump start ground terminal stud point is located on the right side top mount in the engine compartment. Never connect directly to the startup battery negative terminal when connecting a slave power supply to the vehicle, the BMS control module can be damaged.

The startup battery is positioned in the luggage compartment floor and is secured in position with a clamp plate. The startup battery supplies electrical power to the Battery Junction Box (BJB). The BJB contains megafuses, delivering power to the:

Starter motor
Generator
Rear Junction Box (RJB)
Passenger Junction Box (PJB)
Left and right Engine Junction Boxes (EJBs).

A Battery Monitoring System (BMS) control module is mounted on the startup battery negative terminal and provides startup battery status information for the Body Control Module/Gateway Module (BCM/GWM).

The BJB is located below the luggage compartment floor panel, adjacent to the startup battery. The RJB is located on the right side of the luggage compartment behind the trim panel. The BJB and RJB contain fusible links, fuses, and relays to distribute electrical power supply to various vehicle systems. The front and rear EJBs are mounted adjacent to the right front suspension top mount in the engine compartment.

A jump start terminal is located below a hinged cover, adjacent to the front EJB. An additional cover with a lanyard protects the terminal when not in use. If jump starting is required, the cover must be removed and the positive (+) jump lead attached securely. The negative (-) jump lead is attached to a jump start terminal stud located on the right side top mount. The cover must be installed to the positive terminal when not in use.

The Voltage Quality Module (VQM) is used to prevent the vehicle electrical systems being subjected to undesirably low voltages. Low voltages can occur during repeated engine restarts and produces a constant output voltage during engine restart operation. If the electrical systems are subject to low voltages the customer may notice degraded performance of components and systems and incorrect fault Diagnostic Trouble Code (DTC) may be stored.

The PJB is located behind the A-pillar lower trim panel on the passenger side and receives its main power supply from the BJB.

The BCM/GWM is located adjacent to the PJB, and it is the main controller of the vehicle body systems. The BCM/GWM controlled functions are outlined in the relevant articles.

The BCM/GWM software will monitor the state of charge of the startup battery and will determine when an auto stop/start event can occur. It can also intervene to maintain vehicle systems by keeping the engine running or initiating a restart. This can occur due to, for example, climate control system requirements or request for restart from the Powertrain Control Module (PCM). A brake pressure signal is received from the PCM which will indicate to the BCM/GWM that an engine restart is required from driver operation of the foot brake. For additional information, refer to: STARTING SYSTEM