Chery A11 2003 Repair Manual page 254

Maintenance Manual for Chery·Windcloud
3. Coolant Temperature Sensor TF-W
Purpose: this sensor is designed to provide
coolant temperature information. To provide
engine ECU with water temperature signal
used for control of ignition timing and fuel
injection pulse width in startup, idle speed
and normal operation. The main function of
water temperature sensor is to provide
engine with fuel injection pulse width signal
during cold starting. The sensor also sends
signals to control fan operation.
Composition and principle: this sensor is a
thermistor of
coefficient (NTC) with resistance value
decreasing with the increasing of coolant
temperature except linear relation. The said
thermistor is installed in a heat-conducting
sleeve. ECU monitors water temperature
variation by converting resistance value of
thermistor into a changing votage through a
bleeder circuit (inner structure of ECU).
Failure diagnosis:
temperature is higher than allowed upper
limit or lower than lower limit, failure mark
of the knock sensor is set, engine fault
indicating lamp goes on and engine works in
failure mode. In this case ECU controls
ignition and fuel injection according to set
water temperature for failure mode, at the
same time the fan is running at high-speed
mode (normal fan control for system with
fan controlled by a thermal switch).
Limiting data: 2.5±5%KΩ
Installation hint: tightening torque is 15Nm
in maximum.
Hints: the vehicle is equipped with 2 water
temperature sensors, one is single-pin water
temperature sensor, providing the water
temperature gauge with water temperature
signal; the other is double-pin, providing the
engine ECU with water temperature signal.
Caution: the two water temperature sensors
have different resistance values.
negative temperature
When coolant
Coolant temperature sensor
Water temperature sensor
Circuit diagram of coolant temperature sensor
Pins: this sensor has 3 pins, which can
interchange for use.
1 coolant temperature sensor signal (ECU
54#)
2 sensor signal ground (ECU 62#)
Troubleshooting: mainly check if there is
short circuit or open circuit on the
connection between 2 lines on senosr and
ECU connector.
If there is short circuit, open circuit or
grounding between sensor wire harnesses.
Line grounding or defect grounding is liable
to cause engine water temperature gauge to
indicate excessive temperature.
Check to see if ECU connector is loose.
Make sure the connector is in good
condition, for internal looseness may occur
to ECU connector.
Marelli EFI System
3