Coolant Temperature Sensor: Open Or Short Circuit Detected - Yamaha YZF-R25 Service Manual

Fault code No.
Item
2 Connection of main switch cou-
pler.
Check the locking condition of
the coupler.
Disconnect the coupler and
check the pins (bent or broken
terminals and locking condition
of the pins).
3 Wire harness continuity.
4 Malfunction in ECU.
Fault code No. 21
Fault code No.
Item
Fail-safe system
Diagnostic code No.
Tool display
Procedure
Probable cause of malfunc-
Item
tion and check
1 Connection of coolant tempera-
ture sensor coupler.
Check the locking condition of
the coupler.
Disconnect the coupler and
check the pins (bent or broken
terminals and locking condition
of the pins).
2 Connection of ECU coupler.
Check the locking condition of
the coupler.
Disconnect the coupler and
check the pins (bent or broken
terminals and locking condition
of the pins).
19
Black/red lead of the ECU: a break or disconnection of the black/red
lead of the ECU is detected.
Improperly connected → Con-
nect the coupler securely or re-
place the wire harness.
Open or short circuit → Replace
the wire harness.
Between ECU coupler and main
switch coupler.
black/red–black/red
Between main switch coupler
and diode 3 coupler.
blue/yellow–blue/yellow
Between diode 3 coupler and
battery.
black–black
Replace the ECU.
Refer to "REPLACING THE
ECU (engine control unit)" on
page 8-81.
21

Coolant temperature sensor: open or short circuit detected.

Able to start engine
Able to drive vehicle
06
When engine is cold: Displays temperature closer to air temperature.
When engine is hot: Displays current coolant temperature.
Compare the actually measured coolant temperature with the meter dis-
play value.
Maintenance job
Improperly connected → Con-
nect the coupler securely or re-
place the wire harness.
Improperly connected → Con-
nect the coupler securely or re-
place the wire harness.
8-44
FUEL INJECTION SYSTEM
Turn the main switch to "ON".
Fault code number is not dis-
played → Service is finished.
Fault code number is displayed
→ Go to item 3.
Turn the main switch to "ON".
Fault code number is not dis-
played → Service is finished.
Fault code number is displayed
→ Go to item 4.
Confirmation of service com-
Turn the main switch to "ON".
Fault code number is not dis-
played → Service is finished.
Fault code number is displayed
→ Go to item 2.
Turn the main switch to "ON".
Fault code number is not dis-
played → Service is finished.
Fault code number is displayed
→ Go to item 3.
pletion