SECTION 06: ELECTRICAL
DOB 2490-2789 | X3-45 Commuter PA1605 Maintenance Manual (Final Version) – Sec 06 revised June 2017
25
the display. Use the down arrow to see all the
fault messages.
Once the problem corrected, the DID still shows
the fault as being active. You have to leave the
fault diagnostics
menu, wait approximately 20
to 30 seconds and then return to
fault
diagnostics
to request a new diagnostic of the
electrical system
from the mcm. The DID
should display the fault as being inactive. The
mcm can store up to 20 faults, i.e. the first 10
and the last 10. Middle faults will be erased. If
cb6 breaker is tripped, the fault history will be
erased from the mcm memory.
Note
It is of the utmost importance to have a DID
(driver information display) in working
condition because it is the most important tool
to achieve troubleshooting on a multiplex
vehicle.
FIGURE 25: DRIVER INFORMATION DISPLAY
4.2
PROBING VOLTAGE ON THE
MULTIPLEX CIRCUITS
Some multiplex modules are supplied by 12
volts while others are supplied by 24 volts. The
12-volt or 24-volt information is found on the
modules symbol in the wiring diagram. Before
taking voltage readings to track the source of a
problem, first verify if the module is supplied by
12v or 24v, if not, residual voltage on the module
inputs/outputs can draw an erroneous
conclusion.
Inactive multiplex output = residual voltage of
18% to 33% of supply voltage.
Inactive multiplex input = residual voltage of
50% of supply voltage.
Note
o
Verify on the wiring diagram whether the
voltage is 12v or 24v,
o
For a 12v module: an active voltage would
be 12v or 0v but not in between. If you
measure the intermediate tensions (ex. 6v,
2v, or 4v) this must be interpreted as if the
input or the output is inactive.
o
For a 24v module: an active voltage would
be 24v or 0v but not in between. If you
measure the intermediate tensions (ex.
12v, 4v, or 8v) this must be interpreted as
if the input or the output is inactive.
4.3 CAN
NETWORK
The can network wiring is separated in sections
and uses connectors that are not shared with
other circuits, with the exception of c27. This
allows sections of the network to be isolated to
help locate short-circuit on the can.
In case of short-circuit on the can network, this
affects all the modules and they all act as
“no
response” in the error messages of the
“
electrical system
” menu. To locate a short-
circuit, proceed by disconnecting one module
zone at a time while verifying if this makes
inactive the errors in the modules still
connected. Connector c1 (front electrical &
service compartment) disconnects all the
modules at the rear of the vehicle from the
network. Connector c5 (front electrical & service
compartment) disconnects all the modules from
the entrance door & wiper control panel.
Connector c3 (rear electrical panel) disconnects
all the modules at the rear of the vehicle from
the network.
Example: disconnect c5 and c1 and then verify
the status of the errors. If the front modules (a41
to a46) now give inactive errors, which means
short-circuit is elsewhere than in the front
electrical & service compartment.
4.3.1 Spare CAN
A spare can network is installed between the
front and the rear of the vehicle. It has
connectors installed at each end to facilitate
swapping from the regular can network to the
