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Chery QQ6 (S21) / S12LHD. Manual - part 100

4.3 Parameters of technical features

(1) Data limit

Item

Value

Unit

Rated voltage

Can only be run by ECU

Rated resistance at 20℃

2.5

Ω

Range of running temperature

-30 to +130

℃

Max. measuring current passing the

sensor

Permissible vibration acceleration

600

m/s

4.4 Installation attentions

Coolant temperature sensor is installed on the cylinder body and the copper heat conducted

socket is inserted into coolant. There are thread on the socket, and screw in coolant temperature

sensor onto the threaded hole on cylinder block by the hexagon head of the socket. The maximum

permissible tightening torque is 15Nm.

4.5 Failure effects and judgment method
l Failure effects: starting difficulties etc.
l General cause of the failure: man induced failure.

Simple measurement method:

With the joint removed, turn the digital multimeter to Ohm shift, and then connect the two

meter pens respectively to 1# and 2# pins of the sensor; At 20

, the rated resistance should be

℃

2.5kΩ±5% and the others can be measured out from the characteristic curve in above chart.

Analogue method can also be used when measuring, i.e., dip the working area of the sensor in boiled

water (dip for adequate time), observe the resistance change of the sensor, at this point, the resistance

should fall to 300Ω-400Ω(the actual value depends on the temperature of the boiled water).

Coolant temperature
sensor

5. Knock Sensor

5.1 Function of the sensor:

The knock sensor provides ECU with knock signal. When the engine generates knock, ECU

will control to gradually reduce ignition advance angle to eliminate the knock; when no knock

occurs during certain strokes, ECU will gradually increase ignition advance angle to enable the

engine to obtain max. torque.

5.2 Principle of the sensor:

Knock sensor is a kind of vibrating acceleration sensor and is assembled on cylinder block.

Either single or multiple can be installed. The sense organ of the sensor is a piezoelectric element.

The vibration of cylinder block is transferred to piezoelectric crystal by mass block inside of sensor.

The piezoelectricity crystalloid gets pressure from mass block vibration, producing voltage on two

polar and transferring vibration signals to voltage signal and output it. See the following frequency

response characteristic curve. Because the frequency of knock vibration signal is much higher than

the normal engine vibration signal, the ECU can separate the signal into knock signal and non-knock

signal.

5.3 Attentions

Knock sensor has a hole in the middle, through which it is fastened on the cylinder by a M8 bolt.

For the aluminum alloy block, using long bolt with 30 mm; for the casting iron, using 25mm bolt.

The tightening torque is 20

5Nm. The installation position should ensure that the sensor is liable to

receive vibration signals from all cylinders. Decide the optimal installation position of knock sensor

through modal analysis to the engine body. Generally, for a 4-cylinder engine, the knock sensor is

installed between 2# cylinder and 3# cylinder; for a 3-cylinder engine, it is installed at the center of

2# cylinder. Do not let liquid such as engine oil, coolant, brake fluid and water etc. contact the sensor

long. Use of gasket of any type is not allowed in installation. The sensor must cling to the cylinder

tightly through its metal surface. During wiring of sensor signal cables, do not make the signal

cables resonate; otherwise, they may break. Be sure to prevent turning on of high voltage between 1#

and 2# pins of the sensor; otherwise, damage to the piezoelectric element may occur.

5.4 Effects and judgment method

Failure effects: poor acceleration etc.
l Reasons for general failures: long time contact of liquid such as engine oil, coolant, brake fluid

and water etc. with the sensor, which may corrode the sensor.

l Maintenance precautions: (see installation attentions)
l Simple measurement method: (remove the joint) put digital multimeter at ohm shift, and contact

the No. 1, No. 2 and No. 3 pin with its two meter pens. The resistance value should be more

than 1MΩ¸ under normal temperature. Leave the digital multimeter at millivolt shift, and tap

around the sensor using little hammer, there should be voltage signal output.

6. Electric Throttle Body

6.1 Function:

The electronic throttle body can automatically open or close the throttle according to the

driver’s will to apply the accelerator pedal to let the engine work under the corresponding operating

mode. The electronic throttle has cancelled the conventional throttle guy and the opening of throttle

is controlled by ECU based on the signal from accelerator pedal and other signals (such as A/C,

power assisted steering, back and gearshift etc.) through an electronic step motor inside the

electronic throttle body. In addition to cancel of conventional idle speed by-pass and idle speed step

motor, there are also throttle position sensors on the electronic throttle body to feed back the opening

of the throttle. This suite of throttle position sensor is different from the common one; totally two

suites of throttle position sensors are installed inside the electronic throttle body to monitor

rationality of the signals from the latter; when any problem occurs in a certain signal, ECU can still

use the other suite of signals to work on.

6.2 Working principle:

The throttle driving motor is a micro motor, which is composed of multi steel stators in a circle

and a rotor, with one coil on each steel stator. The rotor is a permanent magnet with a nut at its center.

All stators coils are constantly power on. As long as the direction of current of one coil is changed,

the rotor will turn a certain angle. When the directions of current of all stator coils is changed in a

proper order, a rotating magnetic field is formed, which will drive the rotor made from permanent

magnet rotate along a certain direction. Its principle is just that of a micro direct current motor.

This motor drives a suite of special gear reducing mechanism and a bidirectional spring; when

the system is under power off condition, this mechanism can ensure that the opening of throttle valve

plate maintains at a safe position where is bigger than that for idle speed but not too high, so that the

vehicle can continue to run; if engine ECU has entered this failure mode, when applying the

accelerator pedal, the valve plate of the electronic throttle body will no longer act.

电子节气门

6.3 Failure diagnosis:

ECU can monitor short-circuit and break of coil of the throttle driving motor, and light the engine

failure light in case of such failure to let the engine enter failure mode, when the engine fails to

accelerate, has very poor driving performance and needs maintenance immediately.

7. Oxygen Sensor

7.1 Function of the sensor:

Oxygen sensor is one of the principal sensors on modern autos; it can feed back the mixture

strength by detecting oxygen content in exhaust gas. ECU will correct the mixed gas based on the

Electronic throttle

signals fed back by the oxygen sensor, i.e. control injection pulse-width to let the mixed gas always

maintain an approximately ideal air-fuel ratio (14.7:1).

7.2 Principle of the sensor:

Sensing element of oxygen sensor is a kind of ceramic tube with holes, and outside of tube

walls are surrounded by engine exhaust gas and inside is air. Ceramic sensor element is a kind of

solid state electrolyte with electrical heating tube inside (as shown in the figure).

The operation of the oxygen sensor is achieved by converting the concentration difference of

oxygen ion between inside and outside of the ceramic sensor element to the voltage signal output. It

bears the characteristic of solid electrolyte once the temperature of the ceramic sensor element

reaches 350

. Because of the particularity of its materials, the oxygen ion can pass the ceramic

℃

sensor element freely. Taking advantage of this characteristic, the concentration difference will be

converted to electric potential difference to form electric signal output. If the mixed gas is

comparatively thick, the oxygen ion thickness difference between inside and outside of the ceramic

tube will be higher and the potential difference will also be higher, then a mass of oxygen ion will

move from inside to outside, so, the output voltage is comparatively high (close to 800mV-1000mV);

If the mixed gas is comparatively thin, the oxygen ion thickness difference between inside and

outside of the ceramic tube will be smaller and the potential difference will also be smaller, then just

a few of oxygen ion will move from inside to outside, so, the output voltage is comparatively low

1. Cable 2. Dish washer 3. Insulation bush 4. Protective bush

5. Clamp fitting of heating element 6. Heating rod 7. Contact pad

8. Sensor seat 9. Ceramic probe 10. Protection sleeve

Cross-section view of oxygen sensor

Characteristic Curve of oxygen sensor at 600

tpu

t vo

Excessive air-fuel ratio λ

Content .. 98 99 100 101 ..