Chery Fora (Elara A520). Manual — part 144

CHERY·A21 SERVICE MANUAL ENGINE EFI SYSTEM

15

(Disassemble

the

joint)leave

the

digital

multimeter at ohm shift and contact the No.1
and No. 2 pin of the sensor by its two meter
pens. When it is 20

Rated

℃

the resistance is

2.5kΩ±5%. The other temperature can get
reference from above chart.

3.3 KNOCK SENSOR

1)Exterior drawing and pin

This sensor has three pins; No.1 and No.2 pin
connect with ECU, and No. 3 pin connects with
shield.

2)Purpose: This sensor provides engine

knock information to ECU, and carries
out knock control.

3)Installation position

There is a hole in the middle of knock sensor,
and the sensor is assembled on the block
between No.2 and No.3 cylinder head. For the
aluminum alloy block, using long bolt with
30mm long; for the casting iron, using 25mm
long bolt. And the moment is 20±5Nm.

4)Working principle

Knock sensor is a kind of vibrating acceleration
sensor and is assembled on cylinder block. 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. 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)Normal working temperature: -40--130℃

6)Malfunction phenomenon and diagnosis

method

Chart 3-4 Exterior drawing of knock

sensor

Chart 3-5 circuit diagram of knock

sensor

Knock sensor

CHERY·A21 SERVICE MANUAL ENGINE EFI SYSTEM

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l Malfunction

phenomenon:

badness

accelerating.

l Normal malfunction reason: all kinds of

liquid such as oil, coolant, braking liquid
and water contact with sensor for a long
time and erode the sensor.

l Simple measuring method: (disassemble 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 at normal
conditions. Leave the digital multimeter at
millivolt shift, and tap around the sensor
using little hammer, there should be voltage
signal output.

3.4 OXYGEN SENSOR

1)Exterior drawing and pin

There are 4 pins on this oxygen sensor

No. 1 connect to heating power anode (white)

No. 2 connects to heating power cathode (white)

No. 3 connects to signal cathode (gray)

No. 4 connects to signal anode (black)

2)Installation position: Assemble it on the top

of exhaust pipe.

3)Purpose: The oxygen sensor checks the
oxygen percent in exhaust gases and transfer the
signal to ECU, and ECU will control the fuel
closed loop according to this information. This
will make engine working at its optimum
conditions. And transfer and purify CO, HC,
NO

x

compound in 3-way catalytic converter of

the tail gas maximally.

4)Working principle

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

Chart 3-6 Exterior drawing of oxygen

sensor

Oxygen sensor

Main relay

Chart 3-7 circuit diagram of oxygen

sensor

CHERY·A21 SERVICE MANUAL ENGINE EFI SYSTEM

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tube inside. The working of oxygen sensor is
carried out by transferring the concentration
difference of the oxygen ion outside of ceramic
tube to voltage (100mv—900mv)signal and
output.

5)Working voltage:12—14V

6)Malfunction and diagnosis method

l Malfunction: badness idle speed, badness

acceleration, badness tail gas, over fuel
consume etc.

l Reason: 1, moisture entering inside of

sensor, and when the temperature is
changed

pin

is

broken;

2,

sensor

poisoning( Pb,S,Br,Si)

l Notice: it is forbidden to use cleaning liquid,

oiliness liquid or volatility solid during
service.

l Measuring method: a) disassemble joint,

put digital multimeter to ohm shift, connect
meter pen to No.1(white) and No.2(white)
pins of the sensor. Normally the resistance
value is 1~6Ω. b) Connect the joint and
keep it at idle speed status. When the
oxygen sensor reaches to its working
temperature 350℃, keep digital multimeter
to DC volt shift and connect meter pen to
No.3 (gray) and No.4 (black) pins of sensor.
Now the voltage should be fluctuate
between 0.1- 0.9V quickly (the data also
can be gotten from data flow inspected by
diagnosis meter).

3.5 SPEED

SENSOR

(CRANKCASE

POSITIONING SENSOR)

1)Exterior drawing and pin

No.1pin connects to shield

No.2 and No.3 pin provide signal to ECU.

2)Installation position: on the flywheel plane

at rear of engine.

Chart 3-8 Exterior Drawing Of Speed

Sensor

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Service notice:

l For the inductive engine speed sensor, it is

permitted to take out from its pack before it
is assembled to the auto or testing device
right away.

l Inductive engine speed sensor is assembled

by press in method but not hammer tapping.

l Tightening torque is 8.2Nm. Gas clearance

between inductive engine speed sensor and
pulse disc is 0.8 - 1.2mm.

3)Purpose: Speed sensor provides engine speed,
crankshaft angle and top dead center signal to
ECU. That will control engine ignition and
injection timing.

4)Working principle: The inductive engine
speed sensor work together with pulse disc, it is
used in ignition system without distributor
providing engine speed and crank shaft top dead
center information. Speed sensor is made up of
a permanent magnet and coil outside of magnet.
Pulse disc is a tooth disc with 60 teeth originally
but there are two teeth opening. Pulse disc is
assembled on crank shaft and rotate with
crankshaft. When the tip of the tooth passed the
end of inductive engine speed sensor, the
magnet pulse disc incises the magnetic line of
force, generating rotating speed signal and
output.

5)Working temperature:-40--120℃

Resistance of coil in room T:731--989Ω

6)Malfunction and diagnosis method:

l Malfunction: can not start etc.

l Reason: man failure

l Service notice: use pressing method but not

a hammer to install it.

l Simple measure method: disconnect the

joint, put digital multimeter to ohm shift,
connecting two meter pen to No. 2 and No.

Speed sensor

Chart 3-9 Circuit diagram of speed

sensor