Toyota Corolla (E120) 2002–2008 Repair Manual / Diagnostics / Sfi system / Engine coolant temperature circuit / Circuit description
Toyota Corolla (E120): Circuit description
A thermistor is built in the engine coolant temperature sensor and changes the resistance value according to the engine coolant temperature.
The structure of the sensor and connection to the ecm is the same as those of the intake air temperature sensor.
Hint
: if the ecm detects the dtc p0115, p0117 or p0118, it operates the fail–safe function in which the engine coolant temperature is assumed to be 80 c (176 °F).
|
Dtc no. |
Proceed to |
Dtc detection condition |
Trouble area |
| P0115 | Step 1 | Open or short in engine coolant temperature sensor circuit for 0.5 Seconds |
|
| P0117 | Step 4 | Short in engine coolant temperature sensor circuit for 0.5 Seconds | |
| P0118 | Step 2 | Open in engine coolant temperature sensor circuit for 0.5 Seconds |
Hint
: after confirming dtc p0115, p0117 or p0118, confirm the engine coolant temperature in the ”diagnosis/ enhanced obd ii/data list/all” using the hand–held tester or the obd ii scan tool.
Monitor description
The engine coolant temperature (ect) sensor is used to monitor the engine coolant temperature. The ect sensor has a thermistor that varies its resistance depending on the temperature of the engine coolant. When the coolant temperature is low, the resistance in the thermistor increases. When the temperature is high, the resistance drops. The variations in resistance are reflected in the voltage output from the sensor. The ecm monitors the sensor voltage and uses this value to calculate the engine coolant temperature. When the sensor output voltage deviates from the normal operating range, the ecm interprets this as a fault in the ect sensor and sets a dtc.
Example: when the ecm calculates that the ect is –40 c (–40 °F), or more than 140 c (284 °F), and if either the condition continues for 0.5 Sec or more, the ecm will set a dtc.
Monitor strategy
Typical enabling conditions
Typical malfunction thresholds
Component operating range
Wiring diagram
Other materials:
On–vehicle inspection
1. Inspect air–fuel ratio compensation system
Hint:
you can also check the system by choosing ”data monitor”,
then ”o2 sensor output voltage” on the monitor of the
hand–held tester.
Connect the hand–held tester to the terminal 23 (ox1a)
@ 7 (e1) and 21 (ox1b) @ 7 (e1) of ...
Data list/active test
1. Data list
Hint:
using the data list displayed by the hand–held tester or the obd ii scan tool,
you can read the value of
the switches, sensors, actuators and so on without parts removal. Reading the
data list as a first step
of troubleshooting is one method to shorten diagnostic time.
...
Pre–check
1. Diagnosis system
Release the parking brake lever.
check the warning lights.
When the ignition switch is turned on, check that the abs
warning light and brake warning light goes on for 3 sec.
Hint:
when the parking brake is applied or the level of the brake
fluid is low, the ...