Chery A18. Manual — part 8

Troubleshooting: mainly check if there is short circuit
or open circuit on the connection between 4 lines on
sensor and ECU.

If there is short circuit, open circuit or grounding
between sensor wire harnesses.

Sectional view of intake pressure and
intake air temperature sensor

1 Seal ring

5 Casing

2Stainless steel bushing

6 Pressure bracket

3 PCB

7 Welded joint

4 Sensing element

8 Bonded joint

※Throttle Position Sensor

Purpose: this sensor is designed to provide ECU with
information of throttle angle. As per such information,
ECU obtains engine load information and operating
mode information (for instance: start-up, idle speed,
reverse, part load and full load) as well as acceleration
and deceleration information. This sensor is three-wire
style, and the throttle opening can be detected by ECU
via monitoring voltage variation.

Composition and principle: Consisting of two
compass sliding contact resistors and two sliding
contact arms, throttle position sensor is an angle
sensor that outputs linear signals. The axes of contact
arms are on the same axial line with throttle axis, with
5V power supply voltage US being applied to both
ends of each contact resistor. When throttle turns,
contact arms turn along with it and move on sliding
contact resisters, educing potential of contacts UP as
output voltage. This sensor is actually an angle
potentiometer.

Failure diagnosis: ECU monitors throttle angle, and
detects sensor failure when output signal exceeds
upper or lower limit, in which case engine will work in
failure mode, and fault indicating lamp will go on.

Installation: allowable tightening torque for fastening
screw is 1.5Nm-2.5Nm.

Throttle Position Sensor

Circuit diagram of throttle position sensor

Pins:

1 sensor signal ground (ECU17#)

2 5V power (ECU32#)

3 sensor signal (ECU16#)

Troubleshooting: mainly check if there is short circuit
or open circuit on the connection between 3 lines on
sensor and ECU.

Check to see if there is short circuit, open circuit or
grounding between sensor wire harnesses.

※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.

Composition and principle: this sensor is a
thermistor of negative temperature 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 voltage through a bleeder circuit (inner
structure of ECU).

Failure diagnosis: When coolant 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.

Limiting data: 2.5±5%KΩ

Installation hint: tightening torque is 15Nm in
maximum.

Coolant Temperature Sensor

Circuit diagram of Coolant

temperature sensor

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.

Pins: this sensor has 3 pins, which can interchange for
use.

1 coolant temperature sensor signal (ECU 39#)

2 sensor signal ground (ECU 35#)

3 another line connects water temperature signal of
gauge.

Troubleshooting: mainly check if there is short circuit
or open circuit on the connection between 3 lines,
ECU and gauge on sensor.

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.

※Knock Sensor KS

Purpose: this sensor is designed to provide ECU with
engine knocking information so as to carry out
knocking control.

Composition and principle: knock sensor is a sort of
vibration acceleration sensor, which is fixed on engine
cylinder block. ECU controls engine ignition via
signals detected by pressure-sensing element.

Failure diagnosis: ECU monitors on various sensors,
actuators, power amplification circuits and sensing
circuits. In case any of the following situations occurs,
failure mark of the knock sensor is set.

Knock sensor failure
Knocking control data processing circuit failure
Cylinder-detecting signal is unreliable

After failure mark of knock sensor being set, knocking
closed-loop control is shut down, reducing a safety
angle from the ignition advance angle stored in ECU.
When error frequency cuts down to below setting

KS with cable

1.Knocking

block

2.Casing
3.Piezoelectric

ceramics

4.Contactor
5.Electric

connection

Circuit diagram of knock sensor

value, failure mark restores.

Installation hint: tightening torque is 20±5Nm.

Pins:

1 Knock sensor signal 1 (ECU19#)

2 Knock sensor signal 2 (ECU20#)

Troubleshooting: mainly check if there is short circuit
or open circuit on the connection between 2 lines on
sensor and corresponding ECU pins.

If gasket is added during installation; if tightening
torque is proper.

If there is stitching defect between sensor and cylinder,
or there is foreign matter between them.

※Oxygen Sensor

Purpose: this sensor is designed to provide the
information that if there is surplus oxygen after full
combustion of fuel, which is injected into engine
cylinder in the intake air. ECU, when applying this
information,

can

carry

out

fuel

quantitative

closed-loop control so as to achieve utmost conversion
and purification of the three major toxic elements (HC,
CO and NOX) in the engine exhaust with the
application of three-way catalytic converter.

Composition and principle: the sensing element of
oxygen sensor is a porous ceramic pipe, the outer side
of pipe wall is surrounded by engine exhaust, while
inner side vents to atmosphere. According to inside
and outside oxygen concentration difference, sensor
figures out indirectly fuel injection pulse width, and
then transfers the information to ECU, and the ECU
controls the injection again.

The working voltage of oxygen sensor fluctuates
between 0.1-0.9V, 5-8 variations in 10 seconds is
required; if lower than such frequency value, it shows
that the sensor is aged, and needs replacement. The
said sensor is unrepairable.

Failure diagnosis: ECU monitors on various sensors,
actuators, power amplification circuits and sensing
circuits. In case any of the following situations occurs,
failure mark of the oxygen sensor is set.

Accumulator voltage is unreliable

Oxygen Sensor

Circuit diagram of Oxygen sensor