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Appendix B – Troubleshooting Guide for Multiplex Vehicles
6
Problem/Symptom
Fire alarm telltale light and
audible alarm always ON
and there is no fire or high
temperature in the engine
compartment
The vehicle is parked and
the electrical horn is acti-
vated to indicate a fire in
the engine compartment
but there is no fire
A single light, a group of
LED
lights
or
another
function of the vehicle is
not functioning
No backlighting in the
instrument cluster
The radiator/CAC fans do
not function and the
engine is overheating
Probable Causes
Short-circuited fire sensor or
defective sensor
Short-circuited fire sensor or
defective sensor
The multiplex outputs are
protected in current by an
internal "soft-fuse". When an
output is shorted, it turns
OFF and stays OFF until the
"soft-fuse" is reset
Circuit
breaker
CB10
tripped or fuses F10/F29
blown.
Actions
Prior to start the vehicle, cycle the ignition
key to the ON position, OFF position and
then ON position again and then start the
vehicle. This will deactivate the fire alarm
function. This has to be repeated each
time the vehicle is re-started.
Cycle the ignition key between the ON and
OFF position twice within 3 seconds. This
will deactivate the fire alarm function. This
has to be repeated each time the vehicle
is parked.
Turn the ignition key to the OFF position
and turn to the ON position again. This
resets all "soft –fuses".
is
Check circuit breakers CB2/CB10
Check / replace fuses F10, F29
Check / replace relay R22, R23
You can manually engage the
radiator/CAC fans half speed (50%) or full
speed (100%).
1.
On the Driver Information Display,
select DIAGNOSTICS menu. Select
VEHICLE TESTS submenu and then
ACTIVATE RADIATOR FAN SPEED
50% or ACTIVATE RADIATOR FAN
SPEED 100%.
2.
The DID status line will show TEST to
confirm the forced activation of the
radiator fans. To cancel, turn the
ignition switch to the OFF position or
press ESCAPE button, select STOP
TEST submenu and then press
ENTER
button twice. TEST
disappear from the DID status line.
will
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