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Chery QQ6 (S21) / S12LHD. Manual - part 204

gases as carbon dioxide and water etc. At 300-800

, the conversion efficiency of three

℃

-way

catalytic converter is maximum; with a temperature below this scope, the conversion efficiency will

be very poor, while, with a temperature above this scope, the three-way catalytic converter may be

burnt out. Three-way catalytic converter can exert better conversion efficiency only when the

oxygen sensor works. In control strategies of ECU, there are several protective modes for three-way

catalytic converter, and ECU can protect the three-way catalytic converter by regulating air-fuel ratio

and ignition advance angle.

15. Fan Control

15.1 Function:

In order to abstract heat from engine system and from condenser with A/C turned on, fan

control is affected by the signal to ECU sent by water temperature sensor; When water temperature

is high (above the threshold value set by ECU), the fan will run, and when water temperature is low

(below the threshold value set by ECU), the fan will also run; with A/C turned on, the fan will run at

low speed.

15.2 Composition:

DC electric motor double fan (high and low speed change).

15.3 Installation requirements:

The fan is installed between the rear of radiator and the engine, be careful when installing: not

to damage fin of fan blade, otherwise, running noise of the fan will increase, if serious, it may lead to

sharp fall of heat radiation effect of the engine.

15.4 Failure diagnosis:

Fan control circuit is a short or open circuit to ground;

The fan has failure itself;

Too loud fan noise;

Failure in power supply circuit of fan.

15.5 Troubleshooting:

First, validate whether it is a high speed fan system problem or a low speed fan system problem.

Provided that this is a fan control system problem, use a diagnostic tester to locate the failure point,

and then validate whether it is a short-circuit or a break in control circuit.

Failure symptom: the fan failure may result in rise of engine coolant temperature and poor

refrigeration of A/C system.

15.6. Fan Control:

Turn-on of low gear of fan:

1. Temperature of engine coolant: 96℃-102

;

℃

2. On request for A/C, the fan will start up;

3. When driving speed is too high, the fan will start up;

High speed startup of fan:

1. Engine coolant temperature sensor failure;

2. Air flow meter failure;

3. Engine coolant temperature exceeds 102

℃

Pins:

Main relay

High

speed

relay of fan

Low

speed

relay of fan

Brief sketch map of fan control

Fan motor

1. High speed fan control (corresponds to ECU50#);

2. Low speed fan control (corresponds to ECU68#);

The operating mode of fan after engine stops:

1. Failure of intake air temperature sensor of engine, delay 60s;

2. Failure of intake air temperature sensor of engine, delay 60s;

3. Engine coolant temperature exceeds 100.5

, delay 60s;

℃

4. Engine coolant temperature exceeds 70.5

, delay 60s.

℃

16. Position Sensor of Double Brake Pedal

16.1 Function:

制动开关传感器是将刹车信号送给 ECU，ECU 根据（原文不全）

16.2 Working principle:

Inside the brake switch, there are two mutually independent switches with one normal close and

the other normal open. After applying the accelerator pedal, the former normal close switch turns to

be normal open, while the normal open one turns to be normal close. Both signals will be sent to

ECU to be used to control other systems. Whenever the two signals disaccord, ECU will enter failure

mode, the electronic throttle will not respond when applying the accelerator pedal and the engine

will maintain idle speed working state.

Composition: the double brake switch is installed on the bracket of the brake pedal and contains two

independent switches inside.

Installation requirement: the assembly is installed on the pedal and there is a thread adjusting

mechanism on the switch for stroke adjustment of the switch and effective stroke adjustment of the

brake switch.

17. Clutch Position Sensor

17.1 Function:

Long flame (30)

Main power supply (15)

Double brake switch

Clutch position switch provides ECU with the signal of clutch position, but this signal can only

be used to distinguish between disengaging and engaging positions of the clutch.

17.2 Working principle:

ECU provides clutch position switch with a 12V power supply; when the clutch is under

disengaging state, the power supply will ground and ECU will lose 12V high potential signal, by

which the position of the clutch can be judged.

18. A/C Control

By receiving the A/C signal from A/C switch, ECU can control working of A/C compressor.

ECU also can receive the signals from high and low pressure switches of A/C to ensure safety of A/C

system. When A/C signal is sent to ECU through high and low pressure switches, if the low pressure

switch breaks, ECU will not receive the A/C signal; the compressor is thus unable to work. If A/C

system has a too high pressure, the high pressure switch will break and A/C signal can not be

provided to ECU; so, ECU will immediately cut off the compressor. When system pressure is normal

or a little higher (medium pressure), the medium pressure switch will cut in; thus, ECU can control

the fan to run immediately at high speed to ensure a system pressure within the normal range.

Cut off pressure of the low pressure switch: 0.12Mpa

Cut-in pressure of the medium voltage switch: 1.6Mpa

Cut off pressure of the high pressure switch: 3.2Mpa

Through evaporator temperature sensor of the A/C system, ECU

can also protect the A/C system and prevent evaporator case from

freezing. When the temperature provided by the evaporator

temperature sensor is blow 3.75

, ECU will cut off the

℃

compressor; when the temperature is above this degree, ECU will

automatically engage the compressor to let it work.

on
s

swi

tch

e s

A/C switch

离
合
器
位
置
开
关

开关

高
低
压
开
关

中
压
开
关

Chapter Two Fundamental Principle for Failure Diagnosis of

Electronic Fuel Injection System

1. Failure Information Records

The ECU monitors sensor, actuator, related circuit, malfunction indicator and

battery  voltage  etc.,  and  even  EUC  itself  continuously.  At  the  same  time,  the  ECU
inspect  the  reliability  test  on  sensor  signal  output,  actuator  driving  signal  and  internal
signal  (e.g.:  closed  loop  control,  knock  control,  idle  speed  control  and  accumulator
voltage  control  etc.).  ECU  will  set  the  malfunction  record  on  RAM  malfunction
memory  immediately  once  the  malfunction  or  the  unlikelihood  signal  is  detected.  The
failure information records are stored in the form of diagnostic trouble code (DTC) and
are displayed in the precedence order of occurrence of the failures.

Failures can be divided into “stable state failures” and “random failures” (for example,
caused by transient open circuit of wires or poor contact of inserted parts) by failure
frequency.

2. Failure State

Once duration of occurrence of an identified failure exceeds the given stabilization time
for the first time, ECU will account it as a stable failure and then store it as a “stable
state failure”. If this failure disappears, it will be stored as a “random failure” and
“non-existent”. If this failure is identified again, it will still be a “random failure”, but a
“existent” early failure that will not affect average service of the engine.

3. Failure Types

Short circuit to positive pole of power supply
Short circuit to ground
Open circuit (for the case where there are pull-up resistors or pull-down resistors during
input stage, ECU will recognize failure of open circuit at input port as that of short
circuit to positive pole of power supply or that of short circuit to ground)
Signals can not be used

4. Failure Frequency Counter

For every identified failure, a separate frequency counter numerical value (Hz) will be
set.
This numerical value (Hz) for frequency counter determines the time this failure

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