ELECTRICAL
4222983 Second Edition 4-91
4
6. Measure voltage at B+ 48VDC input at SCU.
Does the multimeter display 48VDC?
YES The PDU voltage output good. Proceed to
the next step.
NO Check PDU to SCU harness and
connections. If harness and connections are
good, printed circuit board in PDU is faulty.
7. Place the key switch in the on position and observe
the SCU power LED.
Does SCU power LED illuminate?
YES 48 VDC input J65-1 is good. Proceed to the
next step.
NO Check connections and measure voltage at
J65-1. If 48VDC is present, SCU is faulty. If
voltage is not present, check har ness and
connections.
8. With the steering yoke centered, check the steering
proximity switches LEDs.
Do the steering proximity switche(s) LEDs
illuminate?
YES The steering proximity switche(s) are good.
Proceed to the next step.
NO Check steering proximity switche(s) harness
and connections. If harness and connections
are good, steering proximity switche(s) are
faulty.
9. With key on, measure AC voltage at steering motor
terminals U, V, and W.
Does multimeter indicate 33VAC (+/- 10%) at all
terminals?
YES The SCU is good. Replace steering motor as
needed.
NO The SCU is faulty. Replace SCU as needed.
Start Circuit–Diesel Engine
Symptom: Machine Will Not Start
IMPORTANT
System requires a minimum of 43VDC in order for the
start circuit to operate properly. Verify system
voltage before performing the following procedure.
1. Turn the key to the run position. Enter the
maintenance mode. Toggle the LCD to the switch
status screen.
Figure 4-72
2. Sit in the seat and observe the digit at position (1).
Does the zero change to a one when the key
switch is move to the start position?
YES Key switch is good. Proceed to next step.
NO The key switch is faulty. Check connections
at switch and/or bench test switch and
replace as needed.
3. Toggle the LCD to the CAN Bus Status Screen.
Figure 4-73
4. Observe the MCU status (2). A flashing display
indicates the controller is not communicating.
Is the MCU communicating with the CAN
system?
YES MCU communication is good. Proceed to the
next step.
NO MCU communication is faulty. Check CAN
line connections.
SWITCH STATUS
000 0001 001
TN2831
1
CAN MCU RCU
OLM TCU SCU
TN2764
2
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