7-24
FUEL INJECTION SYSTEM
Fault code No. 21
Symptom Coolant temperature sensor signal is not received properly.
Fail-safe system Able to start
Able to drive
Diagnostic code No. D06
FI diagnostic tool dis-
play
-20–150°C
Cold engine: Displayed temperature is close to the ambient temperature.
Warm engine: Displayed temperature is the current coolant temperature.
Checking method Check the coolant temperature.
Item Item/components and probable cause Check or maintenance job Checking method
1 Check the connection and locking con-
dition of the coolant temperature sen-
sor coupler.
Disconnect the coupler and check the
pins (bent or broken terminals and
locking condition of the pins).
Poor connection → Properly
connect, repair, or replace.
Set the switch on the
FI diagnostic tool sub-
wire harness to "ON",
and then check the
fault code display.
Fault code number
is not displayed →
Service is finished.
Fault code number
is displayed → Re-
fer to item 2.
2 Check the connection and locking con-
dition of the wire harness ECU coupler.
Disconnect the coupler and check the
pins. (bent or broken terminals and
locking condition of the pins)
Poor connection → Properly
connect, repair, or replace.
Set the switch on the
FI diagnostic tool sub-
wire harness to "ON",
and then check the
fault code display.
Fault code number
is not displayed →
Service is finished.
Fault code number
is displayed → Re-
fer to item 3.
3 Continuity of harness Open or short circuit → Re-
place.
Between coolant tempera-
ture sensor coupler and
ECU coupler
(Brown–Brown)
(Black/Blue–Black/Blue)
Set the switch on the
FI diagnostic tool sub-
wire harness to "ON",
and then check the
fault code display.
Fault code number
is not displayed →
Service is finished.
Fault code number
is displayed → Re-
fer to item 4.
