On-board troubleshooting
14
Defective module
A transmission error can be caused by a defective module. All EKE-
®
modules have
passed a production test procedure and are thus guaranteed to function properly.
However, a module may be damaged during shipment or handling.
To find out whether the transmission error is caused by a defective module, do the
following:
1 Disconnect connectors M1 and M2 from the MVB module and connect the
terminators in their place. The module is no longer connected to the bus.
2 Check the green UB LED. It should be dimly lit when the terminators are connected.
(The yellow UE LED, too, remains on.)
3 If the green ST LED is not lit or blinks only very dimly, the module is defective.
Remove the module from the rack and replace it with a spare one.
If the module was not defective, try resetting the Coach Computer - the problem could
be with the application software of some other module.
If the problem persists, continue with the troubleshooting tips presented in the following
sections.
Physical defect in connectors
A transmission error can be caused by a physical defect, such as oxidation, in the MVB
connectors or in the bus cable.
To find out whether the transmission error is caused by a physical error in connectors,
check the connectors visually. Also, if the terminators are in their place and the green
UB LED is not on, the cable connector is more than likely defective.
If there is no physical error in connectors, continue with the troubleshooting tips
presented in the following sections.
Wrong connection or a loop connection or missing termination
In this situation the yellow UE LED is on, and the green UB LED is blinking faintly. The
transmission error may result from a wrong connection or a loop connection. The
terminator modules might be missing, or in the wrong places, or the Multifunction
Vehicle Bus might have been connected into a loop. Visually check all connections and
terminations.
Missing or defective device
In this situation the yellow UE LED is on, and the green UB LED is either on or blinking
very rapidly. The module is not getting a response from all the ports in its configuration.
The MVB configuration may not match with the connected slave devices, or the slave
devices may be defective. Check all connections, terminations and devices, or
troubleshoot the devices according to their manuals. Try resetting the Coach
Computer.
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