Governor System
72
62 690 05 Rev. E
KohlerEngines.com
NEW UPDATED DESIGN GCU/Harness Diagnostics
and Troubleshooting
A new updated design has been released with a sealed
GCU/wiring harness module assembly, that features a
four pin connector instead of spade or butt connectors.
Ground and Power Test
NOTE: This updated design features a sealed GCU
module wiring harness assembly that is serviced
as an assembly and must
NOT
be separated.
1. Remove 2 screws securing sealed GCU wiring
harness assembly to GCU bracket.
2. Turn ignition key to ON position, inspect LED lights
on GCU board, should indicate solid green and
blinking yellow. If no LED illumination, inspect all
system fuses (10 amp power fuses). If fuses are OK,
proceed to following power/probe test. Turn ignition
key to OFF position.
NEW UPDATED DESIGN GCU Power Test/Probe
Location
G
B
C
D
E
F
H
A
A
E-Gov Jumper Test
Tool
B
Black (Ground -)
C
White
D
Red (+)
E
Application
F
Dark Blue
(Application
Speed Input)
G
Red w/Yellow Tracer
(Speed Input)
H
Engine
3. Install E-Gov Jumper Test Tool (refer to Tools and
Aids) between 4 pin GCU connectors. (Ensure wiring
is retained and away from any hot surfaces.)
4. Using a DVOM set to DC volts, test system for
voltage to GCU. Red meter lead (+) to red wire bullet
of test tool and Black meter lead (-) to black wire
bullet of test tool. Battery voltage should be seen
with key ON. If no voltage is seen, inspect 10 Amp
system fuse.
5. Relocate black (-) negative DVOM lead to battery
ground. If no voltage is seen, inspect and repair
main engine wiring harness. If battery voltage is
seen after relocating meter lead, ground circuit in
harness is open. Trace black ground wire to ground
mounting boss under blower housing and inspect/
repair as needed.
6. With tool installed, start engine. Connect a jumper
wire (technician supplied) to red w/yellow tracer
bullet of tool. Connect other end of jumper wire to
battery 12 volt +. Engine speed should increase.
Remove jumper from red w/yellow tracer bullet of
tool and speed should return to low speed (idle).
7. If speed did increase, refer to equipment
manufacturer’s manual for application speed input
voltage from their controller. (Dark blue wire bullet of
test tool can be used for measuring this input signal
voltage with a DVOM.) If speed did not increase in
test above, perform continuity test below on red w/
yellow tracer (speed input).
New Updated Design Speed Control Input
A
B
A
4 pin connector main engine wiring harness to
GCU wiring harness
B
8 pin customer connector main engine wiring
harness
In New Updated Design system, Speed Control Input
wire (red w/yellow tracer) is located in terminal location
B of 4 pin connector. Using a DVOM, perform continuity
test from pin location B of 4 pin connector to pin location
G of 8 pin customer connector. Continuity should be
seen.
If no continuity, repair/replace main engine wiring
harness.
If continuity is seen, refer to equipment manufacturer’s
manual.
