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START. Output LED's monitor relay condition indicating the
presence of voltage at one of three specific output terminals.
Output circuits do not determine output device integrity so
electrical troubleshooting includes output LED inspection
and conventional device and wire harness integrity testing.
Measure disconnected component impedance, impedance
through wire harness (disconnect at SCM), or by temporarily
"test energizing" the specific component.
Here are the logical troubleshooting steps for the SCM device.
1. Determine the output fault you are trying to resolve
(PTO, START, or ETR).
2. Move key switch to the On position and ensure that
the red power LED is illuminated.
3. Move all input switches to ensure all LED's change
state.
4. Position input devices at appropriate position to
achieve the appropriate output. Use the following logic
chart to determine the appropriate input condition.
Function
Power
In
ON
Neutral
—
Start
—
Run (Off
Unit)
—
Run (On
Unit)
—
Mow
—
Backlap
—
Hi Temp
INPUTS
Start ON
Brake
ON
—
+
O
—
O
O
—
O
O
—
O
O
—
O
O
O
The SCM does not connect to an external computer or hand
held device, can not be re–programmed, and does not record
intermittent fault troubleshooting data.
The decal on the SCM only includes symbols. Three LED
output symbols are shown in the output box. All other LED's
are inputs. The chart below identifies the symbols.
Figure 23
5. If specific output LED is illuminated without
appropriate output function, check output harness,
connections, and component. Repair as required.
6. If specific output LED is not illuminated, check both
fuses.
7. If specific output LED is not illuminated and inputs
are in appropriate condition, install new SCM and
determine if fault disappears.
Each row (across) in the logic chart below identifies input
and output requirements for each specific product function.
Product functions are listed in the left column. Symbols
identify specific circuit condition including: energized to
voltage, closed to ground, and open to ground.
PTO ON
In Seat
Hi Temp
—
O
O
O
O
O
—
O
O
—
—
O
—
O
O
—
22
OUTPUTS
Backlap
Start
ETR
+
+
O
+
O
O
+
O
O
+
O
O
—
+
O
O
O
PTO
O
O
O
+
+
O
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