153 

Yes 

To step 4 

2 

Take out relay of AC compressor, and place ignition switch at “ON”. Check 
voltage of power supply terminal of relay, i.e. 30# and 85# pins and cathode 
of power source is around 12V. 

No Next 

step 

Yes 

Repair or replace 
harness 

3 

Check lines at power supply terminal of relay are opened or shorted to 
ground.  

No 

To step 2 

Yes Replace 

relay 

4 

Check voltage of control terminal of AC compressor relay, i.e. between 86# 
pin of relay and cathode of power source is around 3.7V with the 
multimeter. 

No Next 

step 

Yes 

Repair or replace 
harness 

5 

Check lines of control terminal of AC compressor relay, i.e. 86# pin of relay 
and 70# pin of ECU are opened. 

No Diagnosis 

help 

No.111 Malfunction code: P0646 "voltage of relay control circuit of AC 

compressor too low"   

Serial No.  Operation steps 

Results   

Follow-ups   

1 

Switch on diagnosis instrument and commutator, and place ignition switch 
to “OFF”. 

 Next 

step 

Yes 

To step 4 

2 

Take out relay of AC compressor, and place ignition switch at “ON”. Check 
voltage of power supply terminal of relay, i.e. 30# and 85# pins and cathode 
of power source is around 12V. 

No Next 

step 

Yes 

Repair or replace 
harness 

3 

Check lines at power supply terminal of relay are opened or shorted to 
ground.  

No 

To step 2 

Yes Replace 

relay 

4 

Check voltage of control terminal of AC compressor relay, i.e. between 86# 
pin of relay and cathode of power source is around 3.7V with the 
multimeter. 

No Next 

step 

 
 

 

 

154 

Yes 

Repair or replace 
harness 

5 

Check lines of control terminal of AC compressor relay, i.e. 86# pin of relay 
and 70# pin of ECU are shorted to ground. 

No Diagnosis 

help 

No.112 Malfunction code: P0647 "voltage of relay control circuit of AC 

compressor too high"   

Serial No.  Operation steps 

Results   

Follow-ups   

1 

Switch on diagnosis instrument and commutator, and place ignition switch 
to “OFF”. 

 Next 

step 

Yes 

To step 4 

2 

Take out relay of AC compressor, and place ignition switch at “ON”. Check 
voltage of power supply terminal of relay, i.e. 30# and 85# pins and cathode 
of power source is around 12V. 

No Next 

step 

Yes 

Repair or replace 
harness 

3 

Check lines at power supply terminal of relay are opened or shorted to 
ground.  

No 

To step 2 

Yes Replace 

relay 

4 

Check voltage of control terminal of AC compressor relay, i.e. between 86# 
pin of relay and cathode of power source is around 3.7V with the 
multimeter. 

No Next 

step 

Yes 

Repair or replace 
harness 

5 

Check lines of control terminal of AC compressor relay, i.e. 86# pin of relay 
and 70# pin of ECU are shorted to power source. 

No Next 

step 

Yes Diagnosis 

help 

6 

Check electromagnetic clutch of AC compressor works normally.   

No 

Repair or replace 
electro-magnetic 
clutch 

 
 

 

 

155 

No.113 Malfunction code: P1508 "voltage of control circuit of idling 

speed governor too high"   

Serial No.  Operation steps 

Results   

Follow-ups   

1 

Switch on diagnosis instrument and commutator, and place ignition switch 
to “ON”. 

 Next 

step 

Yes 

To step 4 

2 

Take out connector of idling speed governor (EWD) of the harness, and 
check voltage between 2# pin of this connector and cathode of power 
source is around 12V with the multimeter. 

No 

 
Next step 

Yes 

Repair or replace 
harness 

3 

Check lines at power supply terminal of idling speed governor (EWD) are 
opened and shorted to ground. 

No Next 

step 

Yes Next 

step 

4 

Check resistance between 1# and 2# pins of idling speed governor (EWD) 
is around 17.6Ω under 20  with the multimeter.

℃

 

No Replace 

EWD 

Yes 

Repair or replace 
harness 

5 

Check lines between 1# pin of connector of idling speed governor (EWD) 
and 26# pin of ECU are shorted to power source. 

No Diagnosis 

help 

No.114 Malfunction code: P1651 "malfunction of control circuit of 

engine malfunction lamp (SVS)"   

Serial No.  Operation steps 

Results   

Follow-ups   

1 

Switch on diagnosis instrument and commutator, and place ignition switch 
to “ON”. 

 Next 

step 

Yes Next 

step 

2 

Carry out action testing on malfunction lamp of the engine via “actuator 
action testing” of the diagnosis instrument, and observe it is at OFF status 
or ON status. 

No System 

normal 

Yes 

Repair or replace 
harness 

3 

Check lines at power supply terminal of malfunction lamp of the engine is 
open circuited or shorted to ground. 

No Next 

step 

Yes 

Repair or replace 
harness 

4 

Check lines between pin of control terminal of malfunction lamp and 28# pin 
of ECU is open circuited or shorted to power source or the ground. 

No Next 

step 

Yes Diagnosis 

help 

5 

Check bulb of malfunction lamp is working normally. 

No Replace 

bulb 

 

 
 

 

 

156 

Diagnosis flowchart of M7 system based on malfunction 

Before executing steps of malfunction diagnosis based on malfunction of the engine, carry out 
preliminary inspection:   
1. Confirm malfunction indicator lamp of the engine is working normally;   
2. Check and confirm there is no malfunction information recorded with the malfunction diagnosis 
instrument;  
3. Confirm malfunction claimed by the vehicle owner exists and confirm conditions why this 
malfunction appears. Appearance inspection:   
（

1）Check fuel pipe is leaking; 

（

2）Check vacuum pipe is broken, kinked, or correctly connected;   

（

3）Check inlet pipe is blocked, air leaking, squashed or damaged;   

（

4）Check high tension line of ignition system is broken, aging, and ignition sequence is correct;   

（

5）Check earthing location of harness is clean, firm;   

（

6）Check connector of each sensor, actuator is loosening or poorly contacted. Important: in 

case of above-mentioned malfunctions, carry out care and maintenance accordingly, otherwise it 
will affect following malfunction diagnosis and maintenance.   
Diagnosis help: 1. Confirm the engine is free of malfunction records;   
2. Confirm malfunction that is claimed exists;   
3. Carry out according to above-mentioned steps and find out nothing unusual;   
4. Pay attention to the effect of automobile maintenance, cylinder pressure, mechanical ignition 
timing, fuel conditions on the system during inspection;   
5. Replace ECU and test it.   
If malfunction is eliminated at this time, then malfunction part is in ECU; if malfunction still exists 
at this point, replace for original ECU, and repeat the flowchart, and re-inspect.