B-2 Multiplex Troubleshooting
PA-1628Operator's ManualH3-45 COACH
MULTIPLEX TROUBLESHOOTING GUIDE
Problem / Symptom Probable Causes Actions
Vehicle does not Start from
the dashboard
The Engine Stop pushbutton
located on the rear start panel is
depressed
Main electrical shut-off switch
is in the OFF position
1. Twist and pull the Engine Stop
pushbutton to place it in normal
operating position, check that the main
electrical shut-off switch is in the ON
position and retry cranking from the
ignition switch
2. Start the vehicle from the engine
compartment using the rear start button
Vehicle does not Start from
the dashboard and from the
rear
DL0 (BBUS MUX) network
problem (Multiplex)
Module AE52 not powered or is
defective
Engine ECM does not receive
the ignition signal
Engine ECM is not powered
1. Verify that module AE52 is powered:
a. Check the DIAGNOSTICS menu of
Driver Information Display (DID).
Select VIEW ACTIVE FAULTS and
ELECTRICAL. The message “No
Response ModA52, Active”, indicates
a power problem on the module or a
DL0 (BBUS MUX) network problem.
b. Check / reset circuit breaker CB5
c. Check / replace fuse F65
d. Probe gray connector on module to see
if it is powered.
2. Verify that the engine ECM is powered
and gets the ignition signal
a. Check / reset circuit breaker CB8
Check / replace fuse F74
b. Check / reset circuit breaker CB2
Check / replace fuse F78
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