Group 19, Motor Controls
19-3-4 • CONTROL TROUBLESHOOTING SM 765, Dec ’06
Fault
Code
Fault Name Fault Description Control Troubleshooting
Action
Required
31 "VMN
HIGH"
Wrong voltage on
motor power out-
puts; failure in the
power section or
in the mosfet
driver circuit or in
the motor
MASTER • This test is carried out during initial diag-
nosis and in standby. Possible causes:
• Problem with motor connections or the
motor power circuit; check if the 3
phases are correctly connected; check if
there's chassis ground of the motor to
truck frame.
• Unhook battery at controller and do a
diode check between Batt + and Batt -
(should read .3 to .5 volts)
• Fault in the controller power section.
• Possible bad battery, Excessive voltage
to case of battery.
Replace con-
troller
33 "IDLE
TIME"
Displayed when
the Idle time con-
dition starts
MASTER • The main line contactor open function
starts.
• Any traction inputs (Accelerator, pedal
brake, direction S/W-ON) need to close
the contactor.
37 "CONTAC-
TOR
CLOSED"
Line contactor
power contact
closed at power up
MASTER • Before driving the line contactor coil, the
controller checks if the line contactor is
stuck. The controller drives the bridge
for a while, trying to discharge the capac-
itor bank. If they don't dis charge, the
fault condition is entered. It is suggested
to check the contactor contact, see if it is
mechanically stuck.
38 "CONTAC-
TOR OPEN"
Line contactor
power contact
does not pull in
MASTER • The controller has driven the line contac-
tor, but the contactor did not close.
• The wires to the coil are open or a loose
connection.
• The contact does not pull in properly
53 "STBY I
HIGH"
Wrong voltage in
current sensor
feedback circuit
MASTER • The microprocessors verify if the feed-
back of current sensor device output is
within the zero current window. Possible
causes of the fault.
• Current sensor failure.
• Failure in the controller : if the fault per-
sists, replace the power unit.
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