Chery A15. Manual — part 272

If other power equipments like welding guns
need to be used, the storage battery and ECM
terminals must be disconnected.
Do not pull out the spark plug wire lead to check if
the ignition system is working or not because the fu
sprayed out but not used will burn in the three-way
catalyst and soon cause damage;

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See if the vehicle is equipped with a computerized
anti-stealing device during ECM replacement. If it is,
cut off the power supply to the anti-stealing device
and then proceed to replace the ECM, otherwise, the
new ECM will be locked by the anti-stealing device
and unable to work on other vehicles;
The components shall not be subject to heavy impact
during fixing and unfixing;
Do not take off the ECM cover;
Do not touch the sensor with water or other liquids
while replacing and unfixing the oxygen sensor;
Do not run the fuel pump without fuel for long; do not
run it with fuel in the air;
Most electronic injection components can’t be
repaired and shall be replaced if damaged;
Shielded spark plug and high-voltage cable shall be
used for the system. Unshielded spark plug and high-
voltage cable will not only give off disturbing signals,
but also generate a negative influence on the
ignition coil drive module in the ECM and
even damage the ECM.
Do not operate any engine mechanism
(including the throttle) during engine startup.
The clutch may be detached in cold weather.
If the engine fault indicator light is turned on
during engine running, the cause must be
identified and eliminated as soon as possible.

Do not use leaded gasoline as lead may damage the oxygen sensor and the three-way
catalyst.
Repair as soon as possible in case of abnormal engine oil consumption because some
substances in engine oil may damage the oxygen sensor and the three-way catalyst.
In the case of cylinder burning, stop the car immediately to check and repair because the
air mixture may burn in the exhaust manifold and the oxygen sensor and the three-way
manifold may be damaged in no time. If the ignition trouble can’t be eliminated right
away, the fuel spray nozzle of the cylinder on fire may be cut off temporarily.
Throttle clearance shall not be too small, or the overheated exhaust gas may shorten the
life span of the three-way catalyst.
If the vehicle and engine works at a low speed for long at a temperature lower than 10

°C,

the exhaust pipe may see the accumulation of charcoals and blackening. It is normal and
the accumulated charcoal will disappear some time after high-speed driving. Or proper
measures may be taken to maintain the cooling fluid temperature within a certain range.


4. Work completion
Check and make sure that all circuit fittings and fuel pipeline have been properly
connected and secured;
Repair any damaged pipeline and wrap the damaged parts;
Make sure that the high-voltage cable is properly connected;
Take special care while connecting the storage battery to avoid wrongly connecting the
anode and cathode and make sure that the storage battery fittings are securely fastened.

Section Two. Diagnostic techniques

One. Diagnostic method
1. Objective diagnosis
Use equipment and instrument to measure relevant parameters, analyze engine’s
technical status and find engine faults.
Diagnostic instrument can identify fault locations and display the working status of each
electrical component through data flow parameters.
2. Subjective diagnosis
Subjective judgment can be made based on experience and knowledge according to the
engine’s fault signs and features. Factors include:
A. Visual judgment – exhaust color, color changes of various mixtures due to chemical
reactions, metal color changes due to heating, fuel and water leakage, etc.
B. Acoustical judgment – abnormal noise of the engine
C. Touching judgment – engine vibration and heating
D. Smelling judgment – burned wires and electrical components due to overcurrent,
overheated clutch due to friction, etc.

Two. Diagnosis classification
1. Static diagnosis and dynamic diagnosis
Static diagnosis refers to the diagnosis of engine faults by all means when the engine is
out of operation (e.g. measure the resistance of each electrically controlled components
with a multimeter, measure the crank shaft shifting clearance with a dial gauge and
measure cylinder compression pressure with a pressure gauge, etc).
Dynamic diagnosis refers to the diagnosis of engine faults by all means when the engine
is in operation (e.g. diagnosing engine abnormal noise and vibration by the changes
between various working conditions, observing exhaust colors and diagnosing engine
power while the vehicle is driving, etc).
2. Direct diagnosis and indirect diagnosis
Direct diagnosis refers to the direct reflection of fault modes (e.g. fuel consumption,
torque and cracks, etc) by fault signs, features and parameters.

Indirect diagnosis refers to the mathematic treatment of various parameters to determine
engine fault modes (e.g. engine power and acceleration, etc).
3. Downstream diagnosis and upstream diagnosis
Downstream diagnosis is the troubleshooting mode that starts from the system origin to
system end (e.g. checking for absence of high-voltage sparks: first cylinder upper limit
and crank shaft angle sensor →distributor terminals →wires → ECU input terminals →
ECU output terminals →wires →power magnifier →ignition coil →central high-voltage
cable, check the voltage consecutively).
Upstream diagnosis is the troubleshooting mode that starts from the system end to the
system origin (e.g. central high-voltage cable →ignition coil →power magnifier →wire
→ECM output terminals →ECU input terminals →wires →distributor terminals →first
cylinder upper limit and crank shaft angle sensor, check the voltage consecutively)
Whether downstream or upstream diagnosis is adopted is based on the complication of
the diagnosis object. The principle is that upstream diagnosis is generally adopted for
complicated systems while downstream diagnosis is generally adopted for simple systems.
4. Manual diagnosis and instrument diagnosis
Manual diagnosis is the subjective diagnosis of fault signs and features with simple tools
to determine on fault modes. No equipment and instrument is needed in this case. The
diagnosis result is subjective and easily accepted (e.g. fuel leakage, air leakage, exhaust
color, mechanical vibration and abnormal noise, etc).
Instrument diagnosis is the objective diagnosis of fault locations or various parameters
with diagnostic instrument to determine on fault modes. Instrument diagnosis generates
relatively stable results with only minor changes in control conditions and minor
tolerances and therefore is more accurate (e.g. measuring cylinder compression pressure
with a pressure gauge, checking the piston and sealing between the piston and piston ring
with an air leakage instrument, diagnosing the fault location of engine electrical control
components with a diagnostic instrument, etc).
5. Fault diagnosis and performance diagnosis
Fault diagnosis refers to the identification of engine fault modes and locations by various
diagnosis methods.
Performance diagnosis refers to the diagnosis of engine properties when the engine is free
of faults, e.g. check the engine displacement during annual vehicle checkup; test engine
power, fuel consumption and acceleration during engine test.
6. Troubleshooting flowchart