Chery A15. Manual — part 248
Four. Introduction of ECM system and its functions
1. Computer description
MT20 engine control system is based on the engine control module (ECM).
2. Structure and composition of ECM
12V storage battery power source
Ignition coil A
12V ignition switch power source
Ignition coil B
Ignition system
control
System power source ground wire
Fuel pump relay
Grounding of ignition and fuel
injection
Spray nozzle A
5V reference voltage
Spray nozzle B
System
power
source
management
5V reference voltage feedback
Spray nozzle C
Turning speed and crank shaft
sensor
Spray nozzle D
Fuel supply system
control
Engine cylinder sequence
judgment signal
Idle speed control valve
/H
A
Air intake manifold absolute
pressure sensor
I
A
dle speed control valve
/Lo
Throttle position sensor
I
B
dle speed control vaLve
/H
Cooling fluid temperature sensor
I
B
dle speed control valve
/Lo
Idle speed system
control
Intake air temperature sensor
C
s
harcoal canister cleaning
olenoid valve
Evaporation and
exhaust control
Oxygen sensor
E
s
lectrical cooling (high-
peed) fan relay
Vehicle speed sensor
E
s
lectrical cooling (low-
peed) fan relay
Cooling system
control
System
signal input
Power steering signal
Air conditioner clutch relay
Air conditioner request signal
Air conditioner fan relay
Air conditioner
system control
Air conditioner load signal
Engine speed signal
First evaporator temperature
signal
Engine fault indicator light
Air
conditioner
system
signals
Second evaporator temperature
signal
Serial signal (KW2000)
Diagnosis request signal
Anti-stealing device
control
Communications
and anti-stealing
control
Diagnosis
and anti-
stealing
signals
Anti-stealing device control
signal
Linear EGR control valve
EGR feedback signal
D
el
p
h
i M
T
2
0
E
n
g
in
e
C
o
n
tr
o
l M
o
d
u
le
(
E
C
M
)
*********************
Backup European
Standard III signals
Second oxygen sensor signal
Fuel level sensor signal
Backup
European
Standard III
signals
*******************
3. ECU system functions:
Crank shaft position benchmark and running speed measurement
- The system judges the crank shaft position and engine speed by the signals from 58X tooth to
accurately control the engine ignition and fuel spraying timing.
Speed density measurement method for intake air pressure
- ECM measures and determines the air quantity into the cylinder by the intake air temperature
sensor and air intake manifold pressure sensor and realizes proper air-fuel ratio (AFR) by
controlling fuel supply quantity.
Closed-loop control
- Closed-loop control is adopted for fuel supply to the engine and its idle running; the closed-
loop control advantage is that the system control is able to accommodate any difference of
mechanical components due to manufacturing and wearing so that the integrity of the car is
achieved.
Grouped control
- The system divides the engine’s four cylinders into the two groups of 1-4 and 2-3 for
independent ignition control; grouped control optimizes and simplifies the structure so that the
component costs and manufacturing and processing costs can be reduced.
Fuel injection system
- Speed density method and sequential multi-injection are adopted for the system and the fuel
supply quantity is accurately controlled by the main pulse width and adjusting pulse width for
each engine cycle; and closed-loop control and self-learning functions are enabled.
Ignition control
-
Grouped ignition is adopted by the system;
-
The system uses “discharging immediately after being fully magnetized” logic to precisely
magnetizing and discharging time of control ignition coil.
Idle speed control system
- Functions of closed-loop control, self-learning, high-speed correction, self-adjustment of motor
at idle speed and intelligent reset, etc are adopted for the idle-speed control system as per the
engine running status.
- Stepping motor idle-speed control valve is adopted for the system to realize high-accuracy idle-
speed turning speed control.
- The system will control possible idle speed fluctuations that may occur after headlights, cooling
fans and other electric loads are on. It will optimize the idle speed stability by working on the
ignition advance angle and idle speed valve.
Exhaust emission control
- Three-way catalyst is adopted for the treatment of the engine exhaust before emission;
- ECM uses closed-loop fuel control on the basis of oxygen sensor signals to maximize the
transfer ratio of the catalyst.
Protective functions of the three-way catalyst
- The system features the protective functions of the three-way catalyst. ECM assesses the
temperature of the three-way catalyst as per the engine’s working status. When the temperature
is assessed to be higher than the bearable temperature of the three-way catalyst for long, the
system will automatically start the protective functions of the three-way catalyst to control the
temperature.
Evaporative emission pollutant control
- New-generation charcoal canister solenoid valve is adopted. The system controls the cleaning
speed of the active carbon canister on the basis of the engine running status.
Overvoltage protection
- When there is overvoltage due to charging system troubles, the system will enter the protective
mode to limit the engine turning speed and avoid damage to the ECM.
Driving mileage record
- ECM can record the driving mileage of the car in EEPROM for the convenience of aftersales
service and maintenance; in the case of car speed sensor troubles, the driving performance may
be restricted.
Troubleshooting function
- When the system is at working mode, ECM controls the operation of all components and
monitor them real time. Once any system or component fault is identified, the system will start
“engine fault indicator light” to inform the driver to repair in time.
- In the case of system fault, ECM will start the backup function of “emergency control scheme”.
Communication terminals and protocols
- The system carries out serial communication with external equipment through the
troubleshooting terminal by the KeyWord 2000 protocol.
- Troubleshooting instrument may be connected through the troubleshooting terminal to carry out
troubleshooting and diagnosis of system working status.
Car accessory control
- The accessories adopted for this series of cars include:
- The system controls the engine cooling tank fan
- ECM controls the air conditioner compressor by the relay through the air-conditioner switch
and pressure switch.
Five. Basic principles of ECU control system
1. Control logics of ignition switch
Connected with the storage battery
Turn on the ignition switch for the first time
Turn on the main relay and fuel pump for 1.5 s
Shut off the ignition switch
Reset the system right away
System preset
System shutoff
Turn on the ignition switch
Turn on the main relay and fuel pump for 1.5 s
Shut off the ignition switch
Start the engine
System preset
Shut off the ignition switch
System shutoff
System initialization and preset
System
shutoff
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