Chery SQR 7160 sedan. Manual - part 126

 

load and accelerating/decelerating operating conditions, and carry out fuel injection volume 

control corresponding with throttle opening. Throttle position sensor includes a  

potentiometer, and the moving parts is operated by throttle shaft. During operation, ECU 

supply 5V voltage to sensor and measured parameter is variable of throttle opening from 

minimum to maximum.   

      Operation Operational theory of throttle position sensor is shown as fig 7.   

        (3) TMAP sensor (air intake temperature, pressure sensor) 

        ★ TMAP sensor combined air intake temperature sensor and air intake pressure 
sensor . 

      Air intake pressure sensor is an important sensor, which utilize pressure-resistance effect 
of semi-conductor element,  transferring pressure change in intake manifold to voltage 
change.    

   Air intake temperature sensor is used to measure air intake temperature, which is a 
negative temperature coefficient (NTC) resistance thermo-sensitive element.And the 
resistance decrease with temperature increasing. 

        (4) Crankshaft speed and position sensor 

        This system adopts electromagnetic crankshaft speed and position sensor with inner 
composition of watered magnet round cylinder and coil. Crankshaft speed and position 
sensor are fixed on transmission housing, corresponding with sensor signal gear tooth. 
Sensor signal gear has 60-2 teeth. When 1-4 cylinder is in Top Dead Center position，the 
sensor is at the 20

th

 tooth counting from signal gear absent tooth; and when 2-3 cylinder is 

in Top Dead Center position，the sensor is at the 50

th

 tooth counting from signal gear absent 

tooth.  

 

Fig 7.    Crankshaft speed and position sensor Operation Theory 

1. Crankshaft speed and position sensor    2. Signal gear    3. Corresponding signal with 2nd absent tooth    4. Signal 

        Besides identification of Top Dead Center position，signal can be used by ECU for: 

        -Managing of ignition (ignition advance angle and charging duration)； 

    -generating rotaional speed signal； 

        -Confirming synchronization of each engine revolution by identifying the two absent 
teeth. 

        Under the condition of    other factors not changing, the peak value of sensor output 
voltage  is determined on the distance between crankshaft rational speed and position 
sensor and gear tooth. The clearance between the head of crankshaft rotational speed and 
position sensor and the top of signal gear tooth is 1±0.5mm. 

        (6) Oxygen sensor 

 

        Oxygen sensor is used for detecting the content of oxygen in exhaust, which is a major 
component for ensuring actual air/fuel ratio of engine to approaching theoretical air/fuel 
ratio.  

        Oxygen sensor is mounted on the exhaust front pipe, before 3-way catalyst converter. 
Oxygen sensor mainly consists of a ceramics shell made of zirconium oxidize，on which the 
internal/external surface of closed side is    coated with platinum, with a protect tube out the 
ceramics and a metal housing out the ceramics for protecting.      The external surface of 
zirconium oxidize is exposed to exhaust gas and internal surface is exposed to atmosphere. 

 

 

     

Oxygen sensor operation theory: when temperature is over 300℃，zirconia can separate 

ox ion from of oxygen in the exhaust gas passing through oxygen sensor. If contents of 

oxygen in two sides of oxygen sensor are different, a potential difference between two sides 

will generate. Measuring the potential difference will obtain the difference of oxygen 

contents between two environments (gas air side and exhaust gas side), and then the 

information will be sent to ECU. Due to different voltage is corresponding to different 

air/fuel ratio, ECU can control fuel injection of injector to regulate gas air/fuel mixture, 

making air/fuel mixture approach theoretical value to realize    closed loop control. Under 

fuel cutting-off and engine full load condition, oxygen sensor does not operate, which is 

called open loop.   

Voltage

Rich 

Lean 

excessive air coefficient 

Fig 9 Oxygen Sensor and Performance Character Chart 

ceramics body 2. Protecting tube 3.outer metal shell of sensor 4. heating resistor 

a. signal positive(+) , exposed to air b. signal negative(-) exposed to exhaust gas 

       The oxygen sensor is heated oxygen sensor, which can enter operating mode much 

early. Under normal operating condition, oxygen sensor voltage periodically varies within 

0.1～0.9V. 

     Note: Because lead has inhibitory action to platinum oxidation and   leaded gasoline 

will make oxygen sensor lose function quickly and deteriorate  exhaust gas. Therefore 

leaded gasoline is absolutely forbidden. 

(7) 3-way catalyst converter 

3 way catalyst converter is installed on exhaust, before muffler and can decrease 3 

kinds of pollutants’ content in exhaust gas simultaneously: carbon monoxide (CO), 

unburned hydrocarbon (HC) and oxide (NOX). When the air/fuel ration of engine is 

approaching to theoretical air/fuel ratio, the catalyst efficiency of 3-way catalyst converter 

reaches the maximum. When harmful gas under 300℃～800℃  pass through the center of 3 

way catalyst converter, it will be catalyzed by precious metal on the ceramic element, taking 

oxidizing and reducing reaction, and converts to harmless gas. 

 

    4. Ignition system 

        Ignition system is a grouped electronic control ignition system (1—4 cylinders in one 

group, 2—3 cylinders in the other group). The ignition system is integrated with fuel 

injection system, which is an electronic system with a built-in power supply module, and 

canprovide with all kinds of optimal ignition value Upon input instaneous physical 

parameters related with engine operating condition, all kinds of optimal ignition values can 

be wrote into program via a managing circuit.   

ECU controls 2 primary coils on and off. Secondary coil will generate a high voltage 

due to secondary induction when primary coil current is suddenly cut off, and 1-4 cylinder 

and 2-3 cylinder spark plugs connected to secondary coil final terminal via ignition wire 

will obtain high voltage and therefore firing is achieved.   

Basic ignition advance angle is regulated and determined upon engine coolant 

temperature and air temperature. Under most conditions, ECU dynamically compensate 

basic ignition advance angle upon engine rotational speed and air intake manifold absolute 

pressure to obtain optimum ignition advance angle. Under a very low engine idle speed 

condition, ignition advance angle keep constant.   

        (2) Static state high voltage output ignition coil 

 

Fig 10 Ignition Coil Schematic 

1. Cylinder-1 ignition terminal        2. cylinder-2 ignition terminal    3. cylinder-3

ignition terminal

The system uses a closed magnetic circuit coil packed in a plastic container with a coat 

of epoxy outside, which has special ability of non-electric conduct, mechanicalness, thermal 

characteristic and high temperature resistance. The part of primary coil near iron core 

lessens the flow of magnetic current causing secondary coupling can reach maximum and 

has the following capabilities:   

    - High ignition voltage storage; 

    -High energy transmission performance  of secondary coil; 

    -Long ignition duration;  

- Rapid secondary voltage increasing 

    (3) Knock sensor 

High temperature, mechanical parts aging and wearing, low octane gasoline etc may be 

possible knock causes. Since knock may damage engine, to prevent continuous knock,,