Chery A series. Instruction - page 29

ELECTRONIC CONTROL UNIT

The ECU is located on the left of engine firewall. The ECU handles various signals from the
sensors and controls the actuator so as to achieve the best possible operating condition. Many
extra functions are added as compared with the previous model. While by the usage of a
custom-made circuit board that can achieve many special functions, the integrated functions
are enhanced so that the structure has considerably reduced in size and become much more
compact.
The hard wares in the ECU are as follows:
-16 bit CPU single chip

- 8KB RAM (2KB IRAM + 6KB ERAM)

- 2MB FLASH EPROM (12V programming voltage)

- 2KB SERIAL EEPROM

- 16 CHANNELS 10 MODULES/NO. (A/D) CONVERTER

- 4PWM OUTPUT

- CAN MODULE (CAN2.0B)


The ECU software structure is divided into two parts for data processing:
-The “Application” part obtained the measurement of engineering parameter through sensors

to calculate the control parameters of the fuel injectors, ignition coils and idling speed step
motor for controlling the engine starting.

-The “Basic” part is collecting the data from the sensors and converts it into engineering data.

After that it controls the actuator through the calculated parameter generated by the
“application” software, and manages the self-diagnostic programs of the various sensors and
actuators. In addition, it can also communicate with the externally connected diagnostic
tester through the use of “K” serial cable.


The operating system is capable of ensuring the accurate management of the matters related
with time (such as the management of definite and delay timing) and angles (related to the
engine rotation sequence). This type of management is integrated in the software and
calculated according to the precise priority to ensure the optimization management of the
engine even at its high-speed condition. This type of “modular structure” design allows the
possibility of achieving all kinds of flexibility control and in the mean time not tampering the
overall characteristic of the system.
The following data are transmitted into the ECU:
- Battery voltage
- Absolute pressure sensor in the air intake manifold
- Top dead center
- Throttle valve opening angle position
- Air intake temperature

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- Engine coolant temperature
- Air conditioning operation
- Signal from oxygen sensor
- Knock sensor for the accelerator meter on top of the engine crankshaft housing
The air intake efficiency is obtained by calculating through the processing of absolute
pressure, air intake temperature, engine speed, throttle valve position and other signals, and
help to determine the air intake quantity of the cylinder. The inbuilt power supply module in
the ECU is controlling the following functions:
- To control the injected fuel quantity through the control of opening timing of the fuel
injector
- Idling speed step motor
- Ignition coils of the 4 high voltage outputs
- Check valve for recirculation the gaseous fuel on top of the air intake manifold (carbon
canister)
- Temporary turnoff of the air condition compressor
- Dual speed cooling fan for the engine
- Overheating alarm light in the coolant of the engine
- Malfunction alarm light
Other than these major functions, ECU also controls:
- All the self-diagnostic strategy related to input sensors and output actuators
- Wrong signals restoration strategy works on basically effective input signals

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WORKING PRINCIPLE OF ELECTRONIC FUEL INJECTION

CONTROL AND ACTUATORS

Intake Pressure and Intake Air Temperature

Sensor

Purpose: detects manifold absolute pressure from
0.1~0.2bar and intake air temperature, provides engine
with load information.

Composition and principle: this sensor is composed
of two different sensors (i.e. manifold absolute
pressure sensor and intake temperature sensor), and is
installed above pressurizer.
Pressure-sensitive element inside intake pressure
sensor
detects pressure signal on intake manifold for
injection pulse width control of EFI system. This
sensor also serves as the substitute of load signal
sensor.

Intake air temperature sensing element is a resistor
of negative temperature coefficient (NTC), which is
similar to water temperature sensor with resistance
value decreasing with the increasing of intake air
temperature. And engine ECU monitors the variation
of intake air temperature via a comparison circuit
inside.

Failure diagnosis: The electronic device next to
intake pressure sensor detects sensor circuit troubles
such as open circuit, short circuit and sensor damages,
etc. In case ECU detects any sensor output signal that
goes beyond output characteristic curve, the sensor is
diagnosed as failed by ECU. For example: when
intake pressure is higher than upper limit or lower than
lower limit, ECU detects sensor failure (in case that
intake pressure is lower than lower limit when starting,
ECU is able to recognize the starting condition), and
the engine fault indicating lamp goes on. Under this
condition the engine works in failure mode.

Installation: to be installed on pressurizer.

Circuit diagram of manifold absolute
pressure and intake air temperature sensor

Pins:

1# is grounded (connecting ECU 17#);

2# outputs temperature signal
(connecting ECU 40#);

3# connects with standard 5V power
source (connecting ECU 33#);

4# outputs pressure signal (connecting
ECU 37#).

TMAP

Manifold absolute

pressure and intake air

temperature sensor

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Troubleshooting: mainly check if there is short circuit
or open circuit on the connection between 4 lines on
sensor and ECU.
If there is short circuit, open circuit or grounding
between sensor wire harnesses.

Sectional view of intake pressure and
intake air temperature sensor

1 Seal ring

5 Casing

2Stainless steel bushing 6 Pressure bracket

3 PCB

7 Welded joint

4 Sensing element

8 Bonded joint

Throttle Position Sensor

Purpose: this sensor is designed to provide ECU with
information of throttle angle. As per such information,
ECU obtains engine load information and operating
mode information (for instance: start-up, idle speed,
reverse, part load and full load) as well as acceleration
and deceleration information. This sensor is three-wire
style, and the throttle opening can be detected by ECU
via monitoring voltage variation.

Composition and principle: Consisting of two
compass sliding contact resistors and two sliding
contact arms, throttle position sensor is an angle
sensor that outputs linear signals. The axes of contact
arms are on the same axial line with throttle axis, with
5V power supply voltage US being applied to both
ends of each contact resistor. When throttle turns,
contact arms turn along with it and move on sliding
contact resisters, educing potential of contacts UP as
output voltage. This sensor is actually an angle
potentiometer.

Failure diagnosis: ECU monitors throttle angle, and
detects sensor failure when output signal exceeds
upper or lower limit, in which case engine will work in
failure mode, and fault indicating lamp will go on.

Installation: allowable tightening torque for fastening
screw is 1.5Nm-2.5Nm.

Throttle Position Sensor

Circuit diagram of throttle position sensor

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