93 

 

 

No.054 Quick diagnosis for idling-speed governor EWD   

 

Function: provide idling-speed bypass air route, and control air quantity by changing 
cross-section of the route, realizing closed-loop control over rotating speed while the engine is 
under idling-speed condition; principle: one permanent magnet rotating freely on the shaft within 
idling-speed governor is rigidly connected with one rotating slide block, and could rotating driven 
by the coil, making slide block also rotating. Angular position of slide block determines opening of 
bypass duct, and thus adjusting bypass air quantity. Angular position of slide block is controlled 
by duty ratio of electrical pulse output by electronic controller;   

 

Idle speed actuator   

3. Check voltage value of battery anode and earthing is higher than 
15V?.  

1. Switch on diagnosis instrument, and display voltage value of battery 
cell; when the engine is running under normal operating temperature, 
check voltage is higher than 15V? 

2. When the engine is running under normal operating temperature, 
check voltage displayed on the instrument is lower than 15V?.   

5. Repair or replace the engine; confirm it is repairable.   

4. Check when the engine is running at 20001Vm, and switch on 
head lamp, air conditioner, voltage value of battery cell is higher than 
15V?.  

Till malfunction elimination instructions   

Y 

Y 

Y 

Y 

N 

N 

N 

N

N 

 
 

 

 

94 

Definition of EWD3 pin:   

#4# EWD3-1# pin; 

2#26# EWD3-2# pin;    Simple measuring method: 

1. (Remove the connector) place digital multimeter to ohm position, and two pens are 
respectively connected to 1#, 2# pins of governor; rated resistance is 

17.6Ω±0.6Ω under 

20 ; 

℃

otherwise, replace it;   

2. (Connect the connector) Start the engine, and make it rotate under idling speed; carefully put 
the hands against EWD3, and you feel slight vibration (recommend oscillograph);   

3. When the engine is rotating under idling speed, take off harness connector of idling-speed 
governor, and rotating speed of the engine shall be changed, which indicates that idling-speed 
governor is working normally;   

4. Take out harness connector of idling-speed governor, and measure its terminal voltage via 
multimeter or oscillograph. When the engine is rotating, terminal of harness connector of 
idling-speed governor shall be output with impulse voltage, which indicates that control system 
lines of ECU and idlings-peed governor are faul-free; if idling speed is still not stable at this point, 
with large deviations from specified value, check idling-speed governor. If output without impulse 
voltage, open the air conditioner and test again; if still not, it means that control system lines of 
ECU and idlings-peed governor are malfunction.   

If after installation of governor, too low idling speed, idling-speed-free appears, replace for the 
pad with 0.3-0.5mm thick, and screw down bolt twice, with the first torque as 2N·M, and 7N·M for 
the second, and maximum torque no larger than 7N·M. If the torque is too large, it will cause 
EWD casing deformed, and internal slide block and valve body blocked with above-mentioned 
malfunctions;   

 

No.055 Quick diagnosis for knocking sensor   

 

Function: this sensor is for providing engine knocking information to electronic controller ECU for 
knocking control.   

Principle: knocking sensor is a vibration acceleration sensor, which is installed at engine cylinder 
body. Only one or several sensors installed is ok. Its sensitive element is a piezoelectric crystal, 
to which vibration of cylinder body is transferred via mass block within the sensor, and which will 
generate voltage at two pole faces due to pressure generated from vibration of mass block, and 
transforms vibration signal into voltage signal; 

 
 

 

 

95 

 

 
 

 

 

96 

Definition of sensor pin:   

1#11#    Knocking signal output;   

2#30#  Earthing;  

3#19#  Earthing (shielded) 

Simple measuring method: 

1. (Remove the connector) place digital multimeter to ohm position, and two pens are 
respectively connected to 1#, 2# and 1#, 3# pins of sensor; resistance under normal temperature 
shall be larger than 1MΩ;  

2. Place digital multimeter to MV position, and knock at knocking sensor slightly with a small 
hammer; at this point, voltage signal shall be output;   

Note: please check 3# shielded line is well earthed.   

3. Communicate diagnosis instrument specified by complete vehicle plant with electrical injection 
ECU, and read malfunction data within ECU, thus making judgment over throttle valve position 
sensor;  

 

No.056 Quick diagnosis for stepper motor   

 

Function: provide idling-speed bypass air route, and control air quantity by changing 
cross-section of the route, realizing closed-loop control over rotating speed while the engine is 
under idling-speed condition; 

 

Principle: stepper motor is actuall a miniature motor, and its stator is polyphase coil winding and 
rotor is permanent magnet, through which one spiral axis is threaded, and these two are 
contacted with thread. When stator coil is switched with current, the rotor will rotate towards 
corresponding directions. As rotor and spiral axis are contacted with thread, angular 
displacement of rotor is transformed into linear displacement of spiral axis. Bypass cross-section 
could be changed by front and rear moving of spiral axis. If the rotor rotates fixed angle each 
time, spiral axis will move a certain displacement, i.e. one step. Electronic controller could control 
moving steps of stepper motor by changing coil energization phase to obtain corresponding 
bypass air flow.