Chery A series. Manual - part 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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