4. Knocking sensor
(1) Knocking sensor is a vibration acceleration sensor. Mounted on engine cylinder body. Sensing element of
the sensor is a piezocrystal. Vibration of engine cylinder body is transferred to piezocrystal via mass block in the
sensor. Since pressure generated by vibration of mass block is applied to piezocrystal, it generates voltage on two
polar planes and turns vibration signal into voltage signal for output.5-122Symptom
Poor accelerationPossible cause
Various liquids, such as engine oil, cooling fluid, brake fluid, water etc
contact the sensor for a long time, which cause corrosion to the sensor. Mounting torque: 20 ± 5 N.M
Repair precautions: sensor must be fitted closely to cylinder body with its metal surface, any type of washer
is not permitted for installation. For wiring of sensor signal cables, note that do not let resonance occur to signal
cables, otherwise they might be broken. Energizing of high voltage between sensor 1 # and 2 # pins must be
avoided, otherwise piezoelectric element might be damaged.
(2) Simple measuring method:
(Remove joint) turn digital multimeter to ohm position, connect two meter pens with sensor 1 #, 2 # pin
respectively, its resistance value at room temperature should exceed 1M ohm. Turn digital multimeter to millivolt
position, use a hand hammer to tap near knocking sensor, now voltage signal output should be available.
5. Oxygen sensor
(1) Its sensing element is a ceramic tube, outside is open to exhaust, inside is open to atmosphere. When
temperature of sensing ceramic tube reaches 350°C, it will have the characteristic of solid state electrolyte. Just
utilizing this characteristic, it converts concentration difference of oxygen into electric potential difference, thus
forms electrical signal output. If mixed gas is a bit concentrated, inside and outside oxyanion concentration
difference of ceramic tube is high, electric potential difference is a bit high.
A large number of oxyanions move from inside to outside, output voltage is high (approximate 900mV); if
mixed gas is a bit thin, inside and outside oxyanion concentration difference of ceramic tube is low, electric
potential difference is low, only a small quantity of oxyanions move from inside to outside, output voltage is low
(approximate 100mV).
Possible cause
1. humid water vapor ingresses inside of sensor, temperature
changes rapidly, probe is broken.
2. oxygen sensor "is poisoned". (Pb, S, Br, Si) Symptom
Poor idle speed, poor speedup, tail gas
overproof, too high oil consumption1 2 3 4Oxygen sensor Mounting torque: 40-60 N.m
Repair precautions: it is prohibited to use cleaning fluid, oily liquid or volatile solid on oxygen sensor during
repair.
(2) Simple measuring method:
(Remove joint) turn digital multimeter to ohm position, connect
two meter pens with sensor 1# (white), 2# (white) pin respectively, its
resistance value at room temperature is 1- 6 ohm.
(Connect joint) in idle speed condition, when oxygen sensor
reaches its working temperature of 350°C, turn digital multimeter to
DC voltage position, connect two meter pens with sensor 3# (grey),Engine EFI System-Engine EFI System
Symptom Possible cause
Fail to start Man made faultSpeed sensor1 2 3Fault symptom Common cause
Dischrge overproof, increased oil consumption Man made fault5-1234#(black) pin respectively, now voltage should fluctuate quickly between 0. 1-0. 9V.
6. Speed sensor
(1) Use with oscillator. Oscillator is a fluted disc, originally has 60 teeth, but two teeth are absent. Oscillator
is mounted on crankshaft, and rotates with the crankshaft. When tooth tip passes by sensor end closely, the
oscillator which is made of ferromagnetic material cuts magnetic line of permanent magnet in the sensor, and
generates induced voltage in coil, which is output as rotating speed signal. Mounting torque: 8 ± 2 N.m
Repair precautions: use pressing in instead of hammering method for installation during repair.
(2) Simple measuring method:
(Remove joint) turn digital multimeter to ohm position, connect
two meter pens with sensor 2#, 3# pins respectively, rated resistance
at 20°C is 770-950 ohm.
(Connect joint) turn digital multimeter to AC voltage position,
connect two meter pens with sensor 2 #, 3# pins respectively, start up
engine, now voltage output should be available.
Suggestion: use oscillograph for vehicle use to check.
7. Phase sensor
(1) This sensor consists of a hall sensor and a rotor made of steel plate. Fix hall sensor, mount rotor on camshaft.
Rotor is a 180( range cylindrical face steel blade. When the blade covers hall sensor, high Level signal is output;
otherwise low level signal is output. This differentiates two different upper dead points. Repair precautions: avoid removing end cover as far as possible during repair, so as to avoid ingress of foreign
matter, which might result in abnormal damage of magnetic gate.
(2) Simple measuring method:
(Connect joint) turn on ignition switch but not start up engine, turn digital multimeter to DC voltage position,
connect two meter pens with sensor red, black conductors respectively, ensure reference voltage of 5V is available.
Start up engine, voltage output between green and black conductors should be available.
Suggestion: use oscillograph for vehicle use to check.
8. Idle speed regulator
(1) Idle speed regulator consists of a step motor and a sealing plug on its shaft, sealing plug may generate radial
displacement driven by step motor shaft, position of sealing plug determines extent of opening of by-pass airway,
so as to adjust the size of by-pass air quantity. Position of sealing plug is controlled by ECU output.Fault symptom
Too high idle speed, flameout at idle speedPossible cause
Since interior contamination is severe, regulating element
is blocked and leads to malfunction.
Repair precautions: dust and sand grain will result in damage of idle speed regulator. Intake air should be
filtered by dry air cleaner before entering idle speed regulator, filtration efficiency should exceed 99 %. ToEngine EFI System-Engine EFI System
1 2 3 45-124replacing air cleaner, always ensure that no dirt enters air duct, never
use ungraded air cleaner.
(2) Simple measuring method:
(Remove joint) turn digital multimeter to ohm position, connect
two meter pens with regulator pin 1, 4 and 2, 3 respectively. Rated
resistance between 1, 4 and between 2, 3 at 20°C should be about
43.2 ohm.
9. Fuel injector
(1) ECU energizes coil of fuel injector to form magnetic field force. When magnetic field force increases to
sufficient to overcome pressure of return spring, gravity of needle valve and resultant force of frictional force,
needle valve begins to rise, oil injection process begins. When oil injection impulse cuts off, pressure of return
spring closes needle valve again.
Symptom
Poor idle speed, poor speedup, failure to start
(difficult to start)Possible cause
Since lack of maintenance, gum builds up in
fuel injector and leads to malfunction
Repair precautions:
1. there are many kinds of fuel injector, their appearance is the same, mountable fuel injector may not be the
exactly suitable one, part number of fuel injector used in repair must be consistent with original fuel injector, wrong
replacement is not permitted;
2. To facilitate installation, it is recommended to apply silicon free clean engine oil on O ring surface at upper
part connecting distributing pipe of fuel oil. Pay attention not to let engine oil contaminate fuel injector inside and
jet orifice;
3. To remove and reinstall fuel injector, O ring must be replaced, here do not damage sealing surface of fuel
injector;
4. if fuel injector has two slots, when mount buckle clamp, pay attention not to clamp in the wrong position,
refer to mounting position of original parts;
5. It is strictly prohibited to remove strainer, clean or replace strainer at discretion; 6. after removal, ensure
cleanness of fuel injector holder, avoid foreign matter ingressing the cylinder.
Simple measuring method:
(Remove joint) turn digital multimeter to ohm position, connect two meter pens with fuel injector pins
respectively, rated resistance at 20°C is 11-17 ohm.
Suggestion: use special cleaning analyzer to conduct thorough cleaning for the fuel injector per 20000km.
10. Electric fuel pump
(1) Fuel pump is a vane pump driven by DC motor, is placed in oil tank, immersed in fuel oil, utilizes fuel oil
for heat dissipation and lubrication. Storage battery supplies power to electric fuel pump via oil pump relay, the
relay switches on electric fuel pump circuit only at the time of startup and during operation of engine. When engine
shuts down due to accident, fuel pump stops running automatically.Symptom
Large running noise, poor speedup, failure to start
(difficult to start)Common cause
1. Gum builds up to form insulating layer;
2. Oil pump bushing is blocked with armature;
3. Fuel level sensor assembly is corroded etc.Engine EFI System-Engine EFI System
1. Front cross beam assembly
The front cross beam assembly includes front cross beam left/right support assembly, front cross beam sub-
assembly, front cross beam side support etc. They play a role in front bumper.
2. Left/right longitudinal beam assembly
The left/right longitudinal beam assembly includes left/right longitudinal bean front and mid- block assembly,
energy-absorbing beam big assembly, and left/right front damper support assembly etc.
It is mainly used to install engine left/right suspension, left/right front suspension damper, storage battery and
other accessories. In the outside, it can be equipped with left/right front fender.
3. Radiator cross beam assembly
The radiator cross beam assembly includes radiator left/right post big assembly, radiator lower cross beam big
assembly, radiator central support sub-assembly, and radiator upper cross beam big assembly etc.
It is mainly used to install radiator, condenser, engine hood lock, radiator hood, front bumper, and front
headlight.
4. Front wall lower plate assembly
The front wall lower plate connects to the floor, which separates the engine compartment from the cabin. It
includes front wall frame assembly, front wall lower main plate assembly, brake installation reinforced plate, and
front wall left/right support assembly etc.Fig. 5-2 Engine Compartment Assembly & Front Wall Parts
1. Front cross beam assembly 2. Left/right longitudinal beam assembly
3. Panel left/right support assembly 4. Front wall lower plate sub-assembly 5. Front wall upper assembly
6 Radiator cross beam assemblySurvey -Body Structure7-2123456front wall lower plate assembly, front wall upper assembly, left/right front damper support lower front plate
assembly, and right front damper right-angle support assembly.
It is mainly used to install the pipes and accessories of the brake system and clutch system.
5. Front wall upper assembly
The front wall upper assembly includes left/right hinge base mounting plate big assembly, front wall upper
front cover big assembly, VIN number mounting plate, and front wall upper rear cover big assembly etc.
It forms a high-stiffness frame structure together with the engine compartment assembly and the front wall
lower plate assembly. It can generate strong resistant to the transverse collision and rolling deformation. It can also
separate the engine compartment form the cabin, preventing the odor entering into the cabin. Consequently, it can
isolate the noise, heat and vibration.(2) Floor Assembly The floor assembly is the base work of the main structure. It is a key component that connects various
assemblies and carries the load. The vehicle performance is subject to its strength and stiffness. For the floor
assembly, see the Fig. 5-3.
The floor assembly includes front floor assembly and rear floor assembly. The front floor mid-block goes
through a ridgy channel in longitudinal direction. It can increase the longitudinal rigidity together with the lower
floor longitudinal beam. The space below under the channel is used to install various parts and components, such
as transmission gearshift rod, parking brake cable, discharge pipe with three-way catalytic converter etc. In the
cabin, there is carpet and muffle pad. The floor frame structure is made up of front floor left/right frame, front floor
main plate assembly, front floor mid-bridge assembly, rear frame assembly, rear floor rear block assembly, rear
floor mid-block assembly and longitudinal beam etc. These parts and components provide strong and reliable carry
capacity and ensure that the vehicle meets the strict driving requirement on the body.Fig. 5-3 Floor Assembly
1. Front floor left/right frame 2. Front floor main plate assembly 3. Longitudinal beam rear block 4. Rear frame assembly
5. Rear floor rear block assembly 6. Rear floor mid-block assembly 7. Front floor mid-bridge assemblySurvey -Body Structure7-371
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