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

Air intake manifold absolute
pressure sensor

I
A

dle speed control valve

/Lo

Throttle position sensor

I
B

dle speed control vaLve

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

i M

l 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

Content .. 246 247 248 249 ..