Chery A series. Manual - part 30

Pins: 

1 sensor signal ground (ECU17#) 
2 5V power (ECU32#) 
3 sensor signal (ECU16#) 
 

Troubleshooting: mainly check if there is short circuit 
or open circuit on the connection between 3 lines on 
sensor and ECU.   
Check to see if there is short circuit, open circuit or 
grounding between sensor wire harnesses. 

 

※Coolant Temperature Sensor TF-W 

 

Purpose: this sensor is designed to provide coolant 
temperature information. To provide engine ECU with 
water temperature signal used for control of ignition 
timing and fuel injection pulse width in startup, idle 
speed and normal operation. 

 

Composition and principle: this sensor is a 
thermistor of negative temperature coefficient (NTC) 
with resistance value decreasing with the increasing of 
coolant temperature except linear relation. The said 
thermistor is installed in a heat-conducting sleeve. 
ECU monitors water temperature variation by 
converting resistance value of thermistor into a 
changing voltage through a bleeder circuit (inner 
structure of ECU). 

 

 

Failure diagnosis: When coolant temperature is 
higher than allowed upper limit or lower than lower 
limit, failure mark of the knock sensor is set, engine 
fault indicating lamp goes on and engine works in 
failure mode. In this case ECU controls ignition and 
fuel injection according to set water temperature for 
failure mode, at the same time the fan is running at 
high-speed mode. 
 

Limiting data: 2.5±5%KΩ 

Installation hint: tightening torque is 15Nm in 
maximum. 
 

 

Coolant Temperature Sensor 

Circuit diagram of Coolant 

temperature sensor 

G-9

Hints: the vehicle is equipped with 2 water 
temperature sensors, one is single-pin water 
temperature sensor, providing the water temperature 
gauge with water temperature signal; the other is 
double-pin, providing the engine ECU with water 
temperature signal. 

Pins: this sensor has 3 pins, which can interchange for 
use.   
1 coolant temperature sensor signal (ECU 39#) 
2 sensor signal ground (ECU 35#) 
3 another line connects water temperature signal of 
gauge. 

Troubleshooting: mainly check if there is short circuit 
or open circuit on the connection between 3 lines, 
ECU and gauge on sensor.   
If there is short circuit, open circuit or grounding 
between sensor wire harnesses.   
Line grounding or defect grounding is liable to cause 
engine water temperature gauge to indicate excessive 
temperature. 

 

※Knock Sensor KS 

Purpose: this sensor is designed to provide ECU with 
engine knocking information so as to carry out 
knocking control. 

Composition and principle: knock sensor is a sort of 
vibration acceleration sensor, which is fixed on engine 
cylinder block. ECU controls engine ignition via 
signals detected by pressure-sensing element. 

 

 

 

Failure diagnosis: ECU monitors on various sensors, 
actuators, power amplification circuits and sensing 
circuits. In case any of the following situations occurs, 
failure mark of the knock sensor is set.   
Knock sensor failure 
Knocking control data processing circuit failure 
Cylinder-detecting signal is unreliable 
After failure mark of knock sensor being set, knocking 
closed-loop control is shut down, reducing a safety 
angle from the ignition advance angle stored in ECU. 
When error frequency cuts down to below setting 

 

KS with cable 

1.Knocking

block  

2.Casing  

3.Piezoelectric 

ceramics  

4.Contactor  

5.Electric 

connection

Circuit diagram of knock sensor 

G-10

value, failure mark restores. 

Installation hint: tightening torque is 20±5Nm. 

Pins:  

1 Knock sensor signal 1 (ECU19#) 
2 Knock sensor signal 2 (ECU20#) 

Troubleshooting: mainly check if there is short circuit 
or open circuit on the connection between 2 lines on 
sensor and corresponding ECU pins.   
If gasket is added during installation; if tightening 
torque is proper.   
If there is stitching defect between sensor and cylinder, 
or there is foreign matter between them. 
 

※Oxygen Sensor 

Purpose:  this sensor is designed to provide the 
information that if there is surplus oxygen after full 
combustion of fuel, which is injected into engine 
cylinder in the intake air. ECU, when applying this 
information, can carry out fuel quantitative 
closed-loop control so as to achieve utmost conversion 
and purification of the three major toxic elements (HC, 
CO and NOX) in the engine exhaust with the 
application of three-way catalytic converter. 

Composition and principle: the sensing element of 
oxygen sensor is a porous ceramic pipe, the outer side 
of pipe wall is surrounded by engine exhaust, while 
inner side vents to atmosphere. According to inside 
and outside oxygen concentration difference, sensor 
figures out indirectly fuel injection pulse width, and 
then transfers the information to ECU, and the ECU 
controls the injection again. 

 

 

The working voltage of oxygen sensor fluctuates 
between 0.1-0.9V, 5-8 variations in 10 seconds is 
required; if lower than such frequency value, it shows 
that the sensor is aged, and needs replacement. The 
said sensor is unrepairable. 

 

Failure diagnosis: ECU monitors on various sensors, 
actuators, power amplification circuits and sensing 
circuits. In case any of the following situations occurs, 
failure mark of the oxygen sensor is set.   
Accumulator voltage is unreliable 

 

Oxygen Sensor

Circuit diagram of Oxygen sensor

G-11

Manifold absolute pressure signal is unreliable 
Engine coolant temperature signal is unreliable.   
Injector driver stage failure 
After oxygen sensor failure mark is set, fuel 
quantification closed-loop control is shut down, and 
the primitive fuel injection time stored in ECU is used 
to carry out fuel quantification. 

 

Installation hints: the tightening torque of oxygen 
sensor is 50-60Nm, a layer of rust preventive oil shall 
be applied on oxygen sensor after replacing so as to 
prevent from incapable removal in case of rust. 

 

 

 

Troubleshooting: mainly check if the plug connection 
of several wires on the sensor is in good condition, and 
if there is short circuit or open circuit.   
Generally, sensor damage is caused by plumbum and 
phosphorus poisoning, so pay attention to fuel quality, 
meanwhile excessive consumption of engine oil is 
Oxygen sensor has a cable, the other end of which is 
electric connection. The outside of sensor is wrapped 
with asbestos fireproof covering. 

 

There are 4 pins on the joint: 

1# connecting with heating control (ECU1#); 
2# connecting with heating power and main relay; 
3# connecting with sensor ground (ECU36#); 
4# connecting with signal (+) (ECU18#). 
 

 

※  Electronic Control Unit ECU 

Purpose: ECU is the core of electronic engine control 
system. Sensors sent various signals to ECU for 
electric control, and then ECU controls operations of 
fuel injector and ignition coil, etc. after internal 
calculation, thus controlling working of engine. 
 

Normal operation voltage: 9-16V 

Composition:  it has shielded casing and printed 
circuit board, which integrates lots of electronic 
control units for the control of EFI system. 

 

 

氧传感器内部构造图

 

Interior structure of oxygen sensor

ECU 

G-12