Yamaha MTN850-A 2017 Service Manual page 407

Fault code No.
Item
3-7 [For P0117/P0118] Short circuit
Between wire harness (ECU side) output terminal (green/white) "a" of ECU coupler and any other
ECU coupler terminal "b".
Between sub-wire harness (coolant temperature sensor side) output terminal (green/white) "c" and
output terminal (black/blue) "d".
If there is continuity, replace the wire harness and/or sub-wire harness.
A. Wire harness coupler (ECU side)
B. Sub-wire harness coupler (coolant temperature sensor side)
4 Installed condition of coolant
temperature sensor.
5 Defective coolant temperature
sensor.
6 Malfunction in ECU.
7 Delete the fault code and check
that the engine trouble warning
light goes off.
P0117, P0118
[P0117] Coolant temperature sensor: ground short circuit detected.
[P0118] Coolant temperature sensor: open or power short circuit
detected.
b a
Check for looseness or pinch-
ing.
Improperly installed sensor 
Reinstall or replace the sensor.
Execute the diagnostic mode.
(Code No. 06)
When engine is cold:
Displayed temperature is close
to the ambient temperature.
The displayed temperature is
not close to the ambient temper-
ature  Check the coolant tem-
perature sensor.
Replace if defective.
Refer to "CHECKING THE
COOLANT TEMPERATURE
SENSOR" on page 8-169.
Replace the ECU.
Refer to "REPLACING THE
ECU (Engine Control Unit)" on
page 8-157.
Confirm that the fault code has
a condition of "Recovered"
using the Yamaha diagnostic
tool, and then delete the fault
code.
8-50
FUEL INJECTION SYSTEM
c
Turn the main switch to "ON",
and then check the condition of
the fault code using the mal-
function mode of the Yamaha
diagnostic tool.
Condition is "Recovered"  Go
to item 7 and finish the service.
Condition is "Detected"  Go to
item 5.
Turn the main switch to "ON",
and then check the condition of
the fault code using the mal-
function mode of the Yamaha
diagnostic tool.
Condition is "Recovered"  Go
to item 7 and finish the service.
Condition is "Detected"  Go to
item 6.
Service is finished.
d