B-8 Multiplex Troubleshooting
PA-1628Operator's ManualH3-45 COACH
Problem / Symptom Probable Causes Actions
The vehicle is parked and
the electrical horn is
activated to indicate a fire in
the engine compartment but
there is no fire
Short- circuited fire sensor or
defective sensor
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
A single light, a group of
LED lights or another
function of the vehicle is not
functioning
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
turn the ignition key to the OFF position and
turn to the ON position again. This resets all
"soft fuses"
No backlighting in the
instrument cluster
Circuit breaker CB10 is tripped
or fuse F10/F29 blown
Check circuit breaker CB2, CB10
Check / replace fuse F10, F29
Check / replace relay R22, R23
The radiator/CAC electric
fans do not function and the
engine is overheating
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
FORCE RADIATOR FAN SPEED
50% or FORCE 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
TERMINATE TESTS & FORCED
STATES submenu and then press
ENTER button twice. TEST will
disappear from the DID status line.
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