Precautions; Corrosion Inhibitor; Electronic Modules; Mcm - PREVOST H3-41 Maintenance Manual

2.11 PRECAUTIONS

DANGER
Prior to working on a system inside vehicle,
make sure to cut electrical power and air
supply. A component could be supplied with
electricity even if the ignition switch is set to
the OFF position and/or a component could
be pressurized even if air tanks are emptied.
Always refer to the appropriate wiring and
pneumatic diagrams prior to working on
electrical and/or pneumatic systems.
NOTE
When the ignition switch is set to the OFF
position, the electrical components are not
energized except for the MCM, engine ECU,
transmission ECU, instrument cluster module,
the battery equalizer, the preheater system,
AFSS, the wheelchair lift system and some
Multiplex modules which remain energized
during 15 minutes after the ignition has been
set to the OFF position. Prior to working on one
of these electrical components, set the main
electrical shut-off switch located above the
batteries, on the exterior wall of the main power
compartment to the OFF position.
If the vehicle will not be operated for a long
period (more than
recommended, in order to prevent the batteries
from discharging, to trip main circuit breakers
CB2 & CB6 located on the rear junction panel
to stop the small current drawn by the radio
preset station memory, the MCM memory and
the instrument cluster clock. Note that the radio
station presets will be erased, same thing for
the diagnostic codes history and the instrument
cluster clock will have to be reset.

2.12 CORROSION INHIBITOR

A corrosion inhibitor has been sprayed on
certain electrical components in order to protect
them from corrosion. Refer
SAV00002E at the end of this section for
recommended products and where they are
used.
2 weeks), it is
to procedure
PA1621 Maintenance Manual All Series | Revised Sept 2019
SECTION 06: ELECTRICAL
CAUTION
Never put grease or other product on the
multiplex modules connector terminals.
DANGER
Use sprayed sealer in a well-ventilated area.
Do not smoke. Avoid prolonged contact with
skin and breathing of spray mist.
3.

ELECTRONIC MODULES

3.1

MCM

The MCM (Master Control Module) plays the
role of interface between the engine ECM, the
transmission ECU, the telltale panel module and
other I/O-EA, I/O-EB modules. When a multiplex
module is being replaced, the MCM will inform
the new module of its role and function
accordingly to the vehicle options. The MCM
keeps the back-up program of the vehicle
specific multiplex program. So, a specific MCM
cannot be removed from a vehicle and be
installed on another vehicle.
3.1.1

Replacing the MCM

If the MCM must be replaced, a new MCM, pre-
programmed at the factory specifically for the
vehicle must be ordered. The actual vehicle
identification number (V.I.N) will be needed at
the time of ordering.
1. The vehicle should be connected to a battery
charger.
2. Turn the hazards ON. Doing this will prevent
the vehicle to fall in "sleep" mode after the
normal 15 minutes delay.
3. Set the ignition key to the ON position and
leave it in that position at all time while
performing this procedure.
4. On rear electrical junction panel, trip circuit
breaker CB6.
5. Replace the MCM.
6. Reset circuit breaker CB6.
7. The DID
AUTOPROGRAMMING
PLEASE WAIT" until the reprogramming of
indicates "MUX
I/O MODULE
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