105 

immediately (specific value related to vehicle model), and then reduced to about 1.5V (specific 
value related to vehicle model).   
Diagnosis flowchart for inlet pressure temperature sensor (inlet temperature sensor) 

 

1. Ignition switch closed; remove ECU joint and check earth circuit (30-1) of sensor 

is open circuited or shorted to B+? 

2. Check signal circuit (44-2) of sensor is open circuited, shorted to earth or shorted 

to B+? 

3. Plug in ECU joint, and take out sensor plug, ignition turned on. Check socket 

connector terminal (2-1) has reference voltage of 5V?   

4. Replace intake temperature sensor   

5. Replace ECU 

Completed  

Repairs 

Y 

Y 

Y 

Y

N 

N

N

 
 

 

 

106 

Diagnosis flowchart for inlet pressure temperature sensor (inlet pressure sensor) 

 

1. Any following conditions occur? 

---Vacuum booster or fuel pressure-regulating valve hose loosening or 

damaged  

--- Intake manifold vacuum leaking and throttle valve leaking 

2. Disconnect sensor joint, and connect diagnosis instrument, and ignition 

turned on. Observe absolute pressure displayed on diagnosis instrument is 

3. Check lines between ECU terminal 7 of signal circuit of sensor and sensor 

terminal 4 is shorted circuited to B+?   

4. Check lines between ECU terminal 7 of signal circuit of sensor and 

sensor terminal 4 is open circuited or shorted to earth? 

5. Check lines between ECU terminal 12 of 5V reference voltage and sensor 

terminal 3 is open circuited or shorted to earth or to power source?   

6. Check absolute pressure displayed on diagnosis instrument is 1013hpa 

after the following operations? Ignition switch closed; ECU terminal 7 

shorted circuit to ECU terminal 3; ignition switch turned on

7. Check lines between ECU terminal 30 of earth circuit of sensor and 

sensor terminal 3 are open circuited, shorted to earth or to power source?   

8. With ignition switch turned on, check voltage between earth 

circuit (terminal 1) and reference voltage (terminal 3) is about 5V 

9. Replace manifold intake pressure sensor   

10. Replace ECU   

Completed  

Repairs  

Y 

Y 

Y 

Y 

Y 

Y

N 

N 

N 

N

N

N

N

N

N

Y 

 
 

 

 

107 

 

No.060 Quick diagnosis for water temperature sensor   

 

Function: this sensor is for providing information about engine cooling liquid temperature, so that 
the controller could correct oil injection and ignition accordingly.   
Principle: this sensor is a heat variable resistor of negative temperature coefficient (NTC), with its 
resistance value reduced as the temperature rises, but not as linear relationship. This resistor is 
installed within copper heat guiding sleeve.   

 

 

Definition of sensor pin:   
1#45#  temperature signal output; 
2#30#  earthing. 
Simple measuring method: 
1. (remove the connector) place digital multimeter to ohm position, and two pens are respectively 
connected to 1#, 2# pins of sensor, and rated resistance is 2.5kΩ±5% under 20 , and other 

℃

corresponding resistance values could be measured from characteristic curve above. When 
measuring, use simulation method, specifically, put working area of the sensor into boiling water 
(soak time shall be sufficient), and observe changes of sensor resistance, which shall be 
reduced to 300Ω-400Ω (specific value up to temperature of boiling water); 
2. Check water temperature parameter of engine diagnosis instrument is close to water 
temperature at the time, also with obvious changes; make judgment according to value 
displayed;  

 

Serial No. 

Resistance 

Max. 

Temperature tolerance 

Temperature tolerance 

Min. 

Min.

Max.

Temperature  

 
 

 

 

108 

Diagnosis flowchart for cooling liquid temperature sensor 

 

1. Ignition switch closed: take out ECU joint and check earth circuit of sensor (2 pin – 30 pin) 

is open circuited or shorted to B+?   

2. Check signal circuit of sensor (1-45) is open circuited, shorted to B+ or shorted to ground?

3. Plug in ECU joint, turn on ignition and check there is 5V reference voltage between two 

terminals of sensor joint?   

4. Replace cooling liquid temperature sensor of the engine   

Repairs  

5. Replace ECU 

Completed 

Y 

Y 

Y 

Y 

N 

N 

N