ENGINE COMPARTMENT CONNECTION UNIT
Fault finding - System operation87G
87G-8V7 MR-372-J84-87G050$110.mif
UPC
Vdiag No.: 48, 4CENGINE COMPARTMENT CONNECTION UNIT
Fault finding - System operation
General operation
The Protection and Switching Unit is involved in the following functions:
–Access - Safety.
–Air conditioning.
–Lighting.
–Wipers.
–Charging circuit.
–Oil pressure detection.
–Electric power distribution.
1 - Electric power distribution
The main function of the Protection and Switching Unit is to switch and distribute the power supply to the vehicle's
systems, actuators or computers.
Part of this function is handled within the unit, but it is not electronically controlled by the computer.
+ 12 V battery feed
The Protection and Switching Unit receives energy from the battery via the Busbar and MM connectors (tracks 6 and
4) and redistributes the + 12 V feed.
+ 12 V after ignition
The UCH sends the Protection and Switching Unit the + 12 V after ignition feed request via the multiplex network.
When the Protection and Switching Unit receives this request, it actuates the after ignition relay unconditionally. The
signal is distributed to the sensors, actuators and computers.
2 - Charge circuit
One of the main functions of the Protection and Switching Unit is managing the charge circuit.
Purpose and components:
The main function of the charging circuit is to produce and distribute the electrical energy required to operate the
various electrical consumers on the vehicle (computers, lights, etc.).
It is also used to start the engine.
The main components are a battery, an alternator and a starter motor.
MR-372-J84-87G050$110.mif
