MPI – Troubleshooting
13-10
Code No. 21 Engine coolant temperature sensor system Probable cause
Range of Check
D Ignition switch: ON
D Excluding 60 seconds after the ignition switch is turned to ON or immediately
after the engine starts.
Set conditions
D Sensor output voltage is 4.6 V or more (corresponding to an engine coolant
temperature of –45_C or less) for 4 seconds.
or
D Sensor output voltage is 0.1 V or less (corresponding to an engine coolant
temperature of 140_C or more) for 4 seconds.
D Malfunction of the engine coolant temperature sensor
D Improper connector contact, open circuit or
short-circuited harness wire of the engine coolant
temperature sensor circuit
D Malfunction of the engine-ECU
Range of Check
D Ignition switch: ON
D Engine speed is approx. 50 r/min or more
Set conditions
D The sensor output voltage increases from 1.6 V or less (corresponding to an
engine coolant temperature of 40_C or more) to 1.6 V or more (corresponding
to an engine coolant temperature of 40_C or less).
D After this, the sensor output voltage is 1.6 V or more for 5 minutes.
OK
Check trouble symptom.
Check the engine coolant temperature
sensor. (Refer to P.13-32.)
NG
Replace
OK
Measure at the engine coolant temper-
ature sensor connector A-38.
D Disconnect the connector, and
measure at the harness side.
D Voltage between 1 and earth
(Ignition switch: ON)
OK: 4.5–4.9 V
D Continuity between 2 and earth
OK: Continuity
NG
Check the following connector:
B-62
NG
Repair
OK
Check trouble symptom.
NG
Check the harness wire between the
engine-ECU and the engine coolant
temperature sensor connector.
NG
Repair
OK
Replace the engine-ECU.
Check the following connector:
A-38
NG
OK
Repair
NG
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