Chery A18. Manual — part 14

Diagnostic trouble code: P0171 “Self adapting of closed loop control for air fuel
ratio exceeding the upper limit”

(Note: the following diagnostic procedures are applicable only under the
circumstances that the trouble codes of intake air pressure sensor, carbon canister
control valve, oxygen sensor and so on do not appear simultaneously, in case that such
trouble codes appear at same time, overhaul shall be carried out based on the
following procedures after dealing with other malfunctions firstly.)

Item

No.

Operation procedure

Inspection

results

Follow-up

procedure

1

Connect the diagnostic tester and adaptor,
and turn the ignition switch to “ON”
position.

Proceed to next

step.

Yes

Proceed to next

step.

2

Start up the engine, run at idle speed until
the temperature of coolant reaches the
normal value.
Under the full load working condition,
observe the value of “Oxygen sensor
voltage” on the diagnostic tester to verify
that the indicated value is maintained at
100 mV without significant change for
long

time

under

certain

working

conditions.

No

Refer to diagnosis

help.

Yes

Proceed to next

step.

3

Connect the fuel pressure gauge to the
feeding pipe of fuel supply system to
observe whether the fuel pressure is
maintained at 350kPa under full load
working condition.

No

Check and repair

the fuel system.

Yes

Repair and replace
the wiring harness.

4

Verify that the circuits between 36# and
18# pins of ECU and A# (corresponding to
the grey connecting wire of oxygen sensor)
and B# (corresponding to the black
connecting wire of oxygen sensor) pins of
the sensor connector are short to ground.

No

Proceed to next

step.

5

A. Verify that there is quite serious leakage
in the air intake system;
B. Verify that there is blockage in the fuel
injector;
C. Verify that the clearance of spark plug is
excessive large;
D. Verify that the resistance of distributor
circuit is excessive large;
E. Verify that the valve clearance is
excessive large; and etc.

Yes

Carry out service

based on the

diagnostic results.

Diagnostic trouble code: P0172 “Self adapting of closed loop control for air fuel
ratio exceeding the lower limit”

(Note: The following diagnostic procedures are applicable only under the
circumstances that the trouble codes of intake air pressure sensor, carbon canister
control valve, oxygen sensor and so on do not appear simultaneously, in case that such
trouble codes appear at same time, overhaul shall be carried out based on the
following procedures after dealing with other malfunctions firstly.)

Item

No.

Operation procedure

Inspection

results

Follow-up

procedure

1

Connect the diagnostic tester and adaptor,
and turn the ignition switch to “ON”
position.

Proceed to next

step.

Yes

Proceed to next

step.

2

Start up the engine, run at idle speed until
the temperature of coolant reaches the
normal value.
Under the full load working condition
observe the value of “Oxygen sensor
voltage” to verify that the indicated value
is maintained at 900 mV without
significant change for long time under
certain working conditions.

No

Refer to diagnosis

help.

Yes

Proceed to next

step.

3

Connect the fuel pressure gauge to the
feeding pipe of fuel supply system to
observe whether the fuel pressure is
maintained at 350kPa under full load
working condition.

No

Check and repair

the fuel system.

Yes

Repair and replace

the wiring harness.

4

Verify that the circuits between 36# and
18# pins of ECU and A# (corresponding
to the grey connecting wire of oxygen
sensor) and B# (corresponding to the
black connecting wire of oxygen sensor)
are short to power supply.

No

Proceed to next

step.

Yes

Carry out service

based on the

diagnostic results.

5

A. Verify that there is leakage in the fuel
injector;
B. Whether there is air leakage in
exhaust pipe;
C. Whether the ignition timing is correct;
D. Whether the air intake valve conduit
is worn out;
E. Whether the valve clearance is
excessive small;
And etc.

No

Refer to diagnosis

help.

Diagnostic trouble code: P0201 “Circuit malfunction of the 1 cylinder fuel
injector”

Item

No.

Operation procedure

Inspection

results

Follow-up procedure

1

Connect the diagnostic tester and adaptor,
and turn the ignition switch to “ON”
position.

Proceed to next step.

Yes

Proceed to Step 4

2

Disconnect the connector of the 1
cylinder fuel injector on the wiring
harness, and inspect with multimeter to
verify that the voltage between 1# pin of
this connector and the negative grid of
power supply is about 12V.

No

Proceed to next step.

Yes

Repair or replace the

wiring harness.

3

Verify that the circuit between 1# pin of
the connector of the 1 cylinder fuel
injector and the main relay is open, or
short to ground.

No

Proceed to next step.

Yes

Proceed to next step.

4

Inspect with multimeter to verify that the
resistance between 1# and 2# pins of the
1 cylinder fuel injector is within 11~16Ω
under 20

.

℃

No

Replace the fuel

injector.

Yes

Refer to diagnosis

help.

5

Inspect with multimeter to verify that the
voltage between the connector of the 1
cylinder fuel injector (2# pin) and the
negative grid of power supply is about
3.7V.

No

Proceed to next step.

Yes

Repair and replace

the wiring harness.

6

Verify that the circuit between the
connector of the 1 cylinder fuel injector
(2# pin) and 27# pin of ECU is open or
short to ground or power supply.

No

Refer to diagnosis

help.

Diagnostic trouble code: P0202 “Circuit malfunction of the double cylinder fuel
injector”

Item

No.

Operation procedure

Inspection

results

Follow-up

procedure

1

Connect the diagnostic tester and adaptor,
and turn the ignition switch to “ON”
position.

Proceed to next

step.

Yes

Proceed to Step 4

2

Disconnect the connector of the double
cylinder fuel injector on the wiring
harness, and inspect with multimeter to
verify that the voltage between 1# pin of
this connector and the negative grid of
power supply is about 12V.

No

Proceed to next

step.

Yes

Repair and replace

the wiring harness.

3

Verify that the circuit between 1# pin of
the connector of the double cylinder fuel
injector and the main relay is open, or
short to ground.

No

Proceed to next

step.

Yes

Proceed to next

step.

4

Inspect with multimeter to verify that the
resistance between 1# and 2# pins of the
double cylinder fuel injector is within
11~16Ω under 20

.

℃

No

Replace the fuel

injector.

Yes

Refer to diagnosis

help.

5

Inspect with multimeter to verify that the
voltage between the connector of the
double cylinder fuel injector (2# pin) and
the negative grid of power supply is about
3.7V.

No

Proceed to next

step.

Yes

Repair or replace

the wiring harness.

6

Verify that the circuit between the
connector of the double cylinder fuel
injector (2# pin) and 6# pin of ECU is
open or short to ground or power supply.

No

Refer to diagnosis

help.