Chery Fora (Elara A520). Manual — part 153

CHERY·A21 SERVICE MANUAL ENGINE EFI SYSTEM

51

DTC: P0646 Much lower voltage of air conditioner compressor relay control circuit

No.

Operating steps

Result

Follow up steps

1

Connect the diagnostic tester and commutator, put the

ignition switch to “OFF”.

Next step

Yes

To step No.4

2

Take off air conditioner compressor relay; put ignition

switch to “ON”; check the voltage value between relay

power supply ends that relay pin No.30, No.85 and

power cathode and observe if it is around 12V.

No

Next step

Yes

Repair or

replace cable

3

Check if there is open circuit or short circuit to ground of

the relay power supplying ends circuit.

No

To step No.2

Yes

Replace relay

4

Check the voltage value by the multimeter between air

conditioner compressor relay control ends that is relay

pin No.86 and power cathode and observe if it is around

3.7V.

No

Next step

Yes

Repair or

replace cable

5

Check if there is short circuit to ground between the

circuit of air conditioner compressor relay control ends

that is relay pin No.86 and ECU pin No.70.

No

Diagnosis help

DTC: P0647 Much higher voltage of air conditioner compressor relay control circuit

No.

Operating steps

Result

Follow up

steps

1

Connect the diagnostic tester and commutator, put the

ignition switch to “OFF”.

Next step

Yes

To step No.4

2

Take off air conditioner compressor relay; put ignition

switch to “ON”; check the voltage value between relay

power supply ends that relay pin No.30, No.85 and

power cathode and observe if it is around 12V.

No

Next step

Yes

Repair or

replace cable

3

Check if there is open circuit or short circuit to ground of

the relay power supplying ends circuit.

No

To step No.2

Yes

Replace relay

4

Check the voltage value by the multimeter between air

conditioner compressor relay control ends that is relay

pin No.86 and power cathode and observe if it is around

3.7V.

No

Next step

Yes

Repair or

replace cable

5

Check if there is short circuit to power supply between

the circuit of air conditioner compressor relay control

ends that is relay pin No.86 and ECU pin No.70.

No

Diagnosis

help

CHERY·A21 SERVICE MANUAL ENGINE EFI SYSTEM

52

DTC: P1651 Trouble light control circuit failure

No.

Operating steps

Result

Follow up

steps

1

Connect the diagnostic tester and commutator, put the

ignition switch to “ON”.

Next step

Yes

Next step

2

Carry out action test to engine trouble light by using

diagnostic meter “actuator action test” item; and observe

the indicator if it is always at the status of extinguishing or

lighting on.

No

System is

correct

Yes

Repair or

replace cable

3

Check if there is open circuit or short circuit to ground of

the engine trouble light power supplying circuit.

No

Next step

Yes

Repair or

replace cable

4

Check if there is open circuit or short circuit to power

supply or short circuit to ground between the circuit of

engine trouble light control ends and ECU pin No. 28.

No

Diagnosis

help

5. TYPICAL FAILURE AND ITS DIAGNOSIS FLOW

5.1 EXPLANATION

Carry out the primary inspection before start the diagnosing according to the engine failure
phenomenon.

1) Make sure the engine trouble light is working properly;

2) Make sure that there is no failure information record checked by diagnostic meter;

3) Make sure that the failure phenomenon exists according to the customers’ complaints, and

confirm the conditions causing the failure.

Then carry out the exterior inspection:

（1） Check if there is any fuel pipe is leaking;

（2） Check if the vacuum pipe is broken, kinked up or linked correctly;

（3） Check if the air intake pipe is jammed, leaking, staved or damaged;

（4） Check the high voltage line of ignition system if it is broken or aging and if the

ignition order is correct;

（5） Check the cable grounding place if it is clean and fastness;

（6） Check the sensor and actuator joint if it is loosening or bad contact.

Important notice: if the above phenomenon is appeared, you should repair the above the
failure at first otherwise it will influence the later service.

Diagnosis help:1 Confirm there is no engine failure record;

CHERY·A21 SERVICE MANUAL ENGINE EFI SYSTEM

53

2 Confirm that the failure exists before the customer complaints;

3 Inspect the engine according to the above steps and find nothing wrong;

4 During the service please do not ignore the influence from vehicle

maintenance, cylinder pressure, mechanical ignition timing and fuel
conditions;

5 Replace ECU and carry out test. If the failure is deleted, the failure is in

ECU; if the failure can not be deleted, replace back to the original ECU and
repeat the flow and check and repair it again.

5.2 TYPICAL FAILURE DIAGNOSIS FLOW

1. The engine does not rotate or rotate slowly when it is started

The normal failure component: 1) accumulator; 2) starting motor; 3) cable or ignition
switch; 4) mechanical part of the engine.

The general diagnosis flow:

No.

Operating steps

Result Follow up steps

Yes

Next step

1

Check the voltage value between the two wiring terminals

of the accumulator by multimeter; check if it is around

8-12V when the engine is starting.

No

Replace

accumulator

Yes

Next step

2

Put the ignition switch at start position, checking the anode

terminal of starting motor by multimeter and observe the

voltage if it is above 8V.

No

Repair or

replace cable

Yes

Repair or

replace starting

motor

3

Disassemble the starting motor and check its working

conditions. Check if there is open circuit or jammed by

poor lubricating.

No

Next step

Yes

Change to

correct

lubricant

4

If the failure is happened in winter time, check if it is

because of the wrong engine lubricant and gearbox oil

causes the big resistance of the starting motor.

No

Next step

Yes

Repair the

engine inside

resistance

5

Check the mechanical resistance inside of the engine if it is

too big causes the starting motor can not rotate or rotate

slowly.

No

Repeat the

above steps

CHERY·A21 SERVICE MANUAL ENGINE EFI SYSTEM

54

2. The engine can draw rotating but can not start successfully when it is started.

General failure component: 1) no fuel in fuel tank; 2) fuel pump; 3) speed sensor; 4)
ignition coil; 5) engine mechanical part.

Diagnosis flow:

No.

Operating steps

Result Follow up steps

Yes

Next step

1

Connect the fuel pressure meter ( connecting point is

the front end of fuel distributing pipe assembly fuel

intake pipe); starting the engine by starter and check

fuel pressure if it is around 260kpa; take off the

vacuum pipe from fuel pressure regulator check the

fuel pressure if it is around 300kpa.

No

Repair the fuel

supplying

system

Yes

Next step

2

Connect EFI diagnostic meter; observe “engine speed”

data item and start the engine and check if there is

rotation speed signal is output.

No

Repair the

sensor cable

Yes

Next step

3

Pull off one of the cylinder separating line and take off
this cylinder injector joint and connect spark plug to it;

keep the spark electrode around 5mm away from

engine body; start the engine by starter and check if

there is blue and white high pressure fire.

No

Repair the

ignition system

Yes

Eliminate

engine

mechanical

failure

4

Check the pressure of each engine cylinder; check if

there is engine cylinder insufficient pressure.

No

Next step

Yes

Diagnosis help

5

Check if the power supply to ECU pin No.12, 13, 44,

45, 63 is correct; check if the pin armature of No. 3,

51, 53, 61, 80 are working correctly.

No

Check the

corresponding

line