Chery Tiggo T11 LHD. Manual — part 52

Chery T11 Service Manual Electric Injection System

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14. Air Conditioning Control System (A/C)

Principle: Turn on these A/C switches. If both

the A/C pressure and the data detected by the

evaporator temperature sensor are normal, the

A/C request signal will pass through these

switches and get to the ECU. The ECU controls

the A/C relay attracting after it detects this signal.

At the same time, it gives stepper motor a

speed-increasing signal, and switches on the

electronic fan. And the A/C system begins to

operate.

Conditions to switch off A/C system:

1) Throttle position sensor failure;

2) Vehicle speed sensor failure;

3) When the engine is with large load;

4) Evaporator temperature sensor failure;

5) The evaporator temperature is less than

1.5℃;

6) The engine speed is overspeed;

7) The coolant temperature is greater than

108℃;

8) Refueling is too quick.

Trouble Diagnosis:

1) Short circuit of A/C relay wire to earth;

2) Short circuit of A/C relay wire to power

supply;

3) Open circuit of A/C relay wire;

4) Too-low evaporator temperature sensor

temperature;

5) Over-high evaporator temperature sensor

temperature.

Troubleshooting:

1) Examine the wire of A/C system;

2) Examine the damage of A/C system’s

evaporator temperature sensor;

3) Examine the wire jumping inside the

harness.

Circuit diagram of A/C control system

Pin:

No 1 for the A/C request signal (to ECU

39#);

No 2 for the A/C relay control (to ECU 46#).

A/C Request Signal

Power Supply

A/C Compressor Clutch

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15. Fan Control (FAN)

MT 20U controls the fan’s low/high speed. Based on

the water temperature, air conditioning and other

signals, the control system can control the fan’s low

and high speed operation. If the condition is

applicable, the MT 20U will control the fan system

delay.

Control Mode:

For 1

st

gear, the fan is switched on at 98℃ and

switched off at 94℃;

For 2

nd

gear, the fan is switched on at 105℃ and

switched off at 101℃;

If the water temperature is greater than 101℃

after the fan is switched off, the fan continues to

operate for 1 minute;

If the water temperature is greater than 94℃ after

the fan is switched off, the fan continues to

operate for 0.5 minute;

If the water temperature is less than 85℃ after

the fan is switched off, the fan stops;

Trouble Diagnosis:

1) Short circuit of high-speed relay wire to power

supply;

2) Short circuit of high-speed relay wire to earth;

3) Open circuit of high-speed relay wire;

4) Short circuit of low-speed relay wire to power

supply;

5) Short circuit of low-speed relay wire to earth;

6) Open circuit of low-speed relay wire;

Troubleshooting:

In ECU side, examine the short or open circuit of

these wires in accordance with the pins shown in the

left figure.

Circuit diagram of fan control system

In this figure above, the high/low speed

pins are the same as the actual pins. But

the actual circuit diagram is different from

this circuit diagram above. The latter is for

reference only.

Main Power Supply

Dual-Speed Fan

High-speed fan relay

Low-speed fan relay

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16. Definition of ECU Pins

Pin

Connection Point

Type

Pin

Connection Point

Type

1

Ignition switch control fire wire

(supply)

Input

2

Unused

3

Speed signal sensor

Input

4

5V standard power supply

Output

5

5V standard supply earth wire

Earth

6

Front oxygen sensor signal (low level)

Input

7

Unused

8

Unused

9

Unused

10

Unused

11

Diagnosis communication

Output

12

Speed sensor signal (high level)

Input

13

Unused

14

Unused

15

Unused

16

Unused

17

Battery supply (+12V)

Input

18

Battery supply (+12V)

Input

19

Unused

20

5V standard power supply

Output

21

5V standard power supply earth wire

Earth

22

Unused

23

Unused

24

Throttle position sensor signal

Input

25

Unused

26

A/C evaporator temperature sensor

Input

27

Intake manifold temperature sensor

Input

28

Speed sensor signal (low level)

Input

29

Unused

30

Diagnosis request

Input

31

Engine failure lamp

Input

32

Ignition switch 1 and 4

Input

33

Idle stepper motor drive coil B

Output

34

Idle stepper motor drive coil A

Output

35

Unused

36

Unused

37

Unused

38

Rear oxygen sensor signal (low level)

Input

39

A/C request signal

Input

40

Unused

41

Unused

42

Air intake pressure sensor signal

Input

43

Coolant temperature sensor signal

Input

44

Unused

45

Engine speed signal

Output

46

A/C relay control

Output

47

Fuel pump relay control

Output

48

Unused

49

Unused

50

Fan high-speed control

Input

51

Unused

52

Ignition coil 2 and 3

Input

53

Idle stepper motor coil C

Output

54

Idle stepper motor coil D

Output

55

Fuel injector 1#

Input

56

Fuel injector 2#

Input

57

Unused

58

Unused

59

Unused

60

Unused

61

Front oxygen sensor heating control

Input

62

Front oxygen sensor signal (high level)

Input

63

Canister control solenoid valve

control

Input

64

Rear oxygen sensor heating control

Input

65

Unused

66

Unused

67

Fan low-speed control

Input

68

Unused

69

Knock sensor signal

Input

70

Fuel injector 3#

Input

71

Fuel injector 4#

Input

72

Unused

73

Motive earth

Earth

No

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Section Ⅱ Basic Principles of Trouble Diagnosis

1. Basic Principles

1) Failure Information Record

MT 20U electronic control unit continuously detect sensors, actuators, related circuits, failure

lamps, battery voltage and etc, even detect the electronic control unit itself, and conduct the

reliability detection on the sensor output signal, actuator drive signal and internal signal (such

as oxygen closed-loop control, knock control, idle speed control, battery voltage control and

etc.). Once one failure in a certain process occurs, or one signal value is unreliable, the

electronic control unit will immediately set a failure information record in the failure register

of RAM. The failure information record will be stored with the form of failure code, and

displayed in the sequence of failure occurrence.

These failures can be divided into “Stable Failure” and “Chance Failure” (such as the

failures caused by the transient harness short-circuit or the bad contact of connecting parts) in

accordance with their frequency of occurrence.

2) Failure State

If the duration of a identified failure occurrence is initially greater than the setting stabilized

time, the ECU will confirm it is a stable failure, and store it as the “Stable Failure”. If this

failure disappears, it will be stored as “Chance Failure” and “Nonexistent”. If this failure is

identified again, it still be a “Chance Failure”, but a “existent” history failure doesn’t make an

influence on the normal operation of a engine.

3) Failure Type

a. Short circuit to the positive electrode of power supply;

b. Short circuit to earth;

c. Open circuit;

d. Signal unreliable.

4) Four Failure Types

Failures of All Electronic Fuel Injection Vehicle Are Basically Defined As These Types.

a. Max. failure, which means its signal is greater than the upper limit of normal

range.

b. Min. failure, which means its signal is less than the lower limit of normal

range.

c. Signal failure, without signal.

d. Unreasonable failure, with signal, but the signal is unreasonable.