Section 06: ELECTRICAL
PA1553
33
4.8 ESSENTIAL FUNCTIONS TO OPERATE
THE VEHICLE
Even with a defective CECM (Chassis Electronic
Control Module) or a CAN network problem,
essential base functions are maintained to rear
start the vehicle from the engine compartment
and drive in a secure manner.
However, many secondary functions are lost. In
this case, the following directives must be
followed.
o Never connect a battery charger when the
ignition is in the ON position on a vehicle with
a CAN defective or certain functions will start
up by themselves,
o Disconnect the charger before starting the
vehicle, if not the default functions will not
activate,
o If the default mode does not activate, try to
turn the ignition OFF while ensuring that no
charger is connected and then restart the
vehicle.
4.8.1 Available Functions
o Startup: Turn on the ignition in the driver's
area and rear start the vehicle from the
engine compartment,
o Windshield wipers: Wipers functions at 1st
speed only,
o Windshield washer fluid,
o Headlights: Low beams only,
o Directional signals: Rear and front only,
o Stoplights: 2 upper stoplights + high-mounted
stoplight are functional,
o HVAC: Functional with set point fixed at 70°F
(22°C), evaporator and condenser fixed at
speed 1, defroster fixed at speed 4.
4.9 LOWER PRIORITY MODULES FOR
BREAKDOWN SERVICE
Modules A43 (IO-A) and A44 (IO-B) affect lower
priority functions. These modules can therefore
be used as spare parts for breakdown service
while on the road.
Functions lost if A43 is removed and used as
spare part:
o High beams,
o Ability to turn on the parking lights only,
o Driver's area lighting,
o Tag axle activation,
o Courtesy blinkers.
Functions lost if A44 is removed and used as
spare part:
o Fresh air damper mix trap control,
o Driver's area and entrance overhead light,
o Front clearance lights.
4.10 MULTIPLEX MODULES
4.10.1 CECM
The CECM plays the role of interface between
the engine ECM, the Transmission Control
Module TCM, the telltale panel module and
other IO-A, IO-B modules. When a multiplex
module is being replaced, the CECM will inform
the new module of its role and function
accordingly to the vehicle options.
4.10.2 MASTER ID
The Master ID works in conjunction with the
CECM. It keeps the specific back-up program of
the vehicle. So, a specific Master ID cannot be
removed from a vehicle and installed on another
vehicle.
4.10.3 IO-A
IO-A modules receive inputs and control
outputs. IO-A's are used for all outputs of 1 amp
or less.
4.10.4 IO-B
IO-B modules receive inputs and control
outputs. IO-B's are used for outputs up to 30
amps.
4.11 MULTIPLEX MODULES REPLACEMENT
IO-A, IO-B and CECM multiplex modules can be
replaced and reprogrammed without having to
connect a computer to the vehicle.
Lower
screw
FIGURE 19: IO-B MODULE REMOVAL