(f)

Read control system DTC code again to confirm that the
system has no DTC code.

No

Intermittent Fault. Refer to 

2.2.7.3

 

Intermittent

Fault Check

Yes

Step 17

Diagnostic completed.

5. Repair Instructions:

Replace post-catalytic oxygen sensor. Refer to 

2.4.7.1

 

Post-Catalytic Oxygen Sensor Replacement

.

2.2.7.23 DTC P0170 P0171 P0172 P2177 P2178 P2187 P2188

1. DTC Descriptor:

DTC

P0170

Close-Loop Control Down Stream Air-Fuel Ratio Self Learn Unreasonable

DTC

P0171

Close-Loop Control Down Stream Air-Fuel Ratio Self Learn Too Lean

DTC

P0172

Close-Loop Control Down Stream Air-Fuel Ratio Self Learn Too Rich

DTC

P2177

Close-Loop Control Down Stream Air-Fuel Ratio Self Learn Value Higher Than Maximum

DTC

P2178

Close-Loop Control Down Stream Air-Fuel Ratio Self Learn Value Lower Than Minimum

DTC

P2187

Close-Loop Control Down Stream Air-Fuel Ratio Self Learn Value Higher Than Maximum
(Low-Load Zone)

DTC

P2188

Close-Loop  Control  Down  Stream  Air-Fuel  Ratio  Self  Learn  Value  Lower  Than  Minimum
(Low-Load Zone)

Engine  Control  Module  (ECM)  controls  the  close-loop  Air-Fuel  ratio  Measure  system  that  achieves  optimal  combination  of
performance, fuel economy and emissions control. In the close-loop mode, the engine control module monitors heated oxygen
sensor (HO

2

S) signal voltage and adjusts fuel supply according to the signal. Changes in fuel supply will change the value of long-

term and short-term fuel supply adjustment. Short-term fuel supply adjustment will respond to heated oxygen sensor signal voltage
and rapidly change. These changes will fine tune the fuel supply. Long-term fuel supply adjustment will respond to the trend in short-
term fuel supply adjustment. Long-term fuel adjustment adjusts the fuel supply in order to return to the center of the short-term fuel
adjustment value and controls the short-term fuel adjustment. The ideal fuel adjustment value is around 0%. A positive value indicates
that engine control module is increasing fuel supply to compensate the lean Air-Fuel mixture. A negative value indicates that engine
control module is decreasing fuel supply to compensate the rich Air-Fuel mixture.

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Control System JL4G18-D

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2. Conditions For Setting DTC and The Fault Location:

DTC Code

DTC Detection Strategy

Conditions For Setting The DTC

(Control Strategy)

Fault Locations

P0170
P0171
P0172
P2177
P2178
P2187
P2188

1. Fuel Adjustment Value Higher

Than Maximum Limit

2. Fuel Adjustment Value Lower

Than Minimum Limit

3. Fuel Adjustment Value Higher

Than Maximum Limit (Low-Load
Zone)

4. Fuel Adjustment Value Lower

Than Minimum Limit (Low-Load
Zone)

1. Excessive air coefficient is higher

than the standard value 1.23.

2. Excessive air coefficient is higher

than the standard value 0.77.

3. With engine speed at 1,640-3,200

rpm, throttle opens 20% -60%.

4. With engine speed at 1,640-3,200

rpm, throttle opens 20% -60%.

1. Fuel Injectors

2. Canister

3. MAP

4. TPS

5. Pre-Catalytic Oxygen

Sensor

3. Schematic:

Refer to 

2.2.6.1

 

Schematic

.

4. Diagnostic Steps:

Note

Before carrying out this diagnosis step, observe the data list on scan tool and analyze the accuracy of the data, as
these will help with quick diagnosis.

Step 1

Check there are no other control system DTC codes.

(a)

Connect scan tool to the datalink connector.

(b)

Turn the ignition switch to "ON" position.

(c)

Press the scan tool power button.

(d)

Select the following menu items: Engine/Read DTC codes.

(e)

Read DTC codes.

Are there DTC codes other than P0170, P0171, P0172, P2177,
P2178, P2187, P2188?

Yes

Refer to 

2.2.7.11

 

DTC Code Index

No

Step 2

Read the intake manifold absolute pressure sensor data.

(a)

Turn the ignition switch to "OFF" position and connect scan
tool.

(b)

Start the vehicle.

(c)

Read the intake manifold absolute pressure sensor data.

(d)

Read the scan tool for atmospheric pressure value, and
compare it with table

2.2.1.3

 

Altitude and Atmospheric

Pressure Correlation

.

Is scan tool atmospheric pressure reading normal?

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No

Refer to 

2.2.7.17

 

DTC P0105 P0106 P0107

P0108

Yes

Step 3

Read the throttle position sensor data.

(a)

Start the vehicle.

(b)

Warm up the engine with normal idle speed and throttle
opening is less than 10%.

(c)

Use scan tool to read throttle position sensor data.

Is throttle position sensor data normal?

No

Refer to 

2.2.7.20

 

DTC P0122 P0123

Yes

Step 4

Read the pre-catalytic oxygen sensor data.

(a)

Start the vehicle.

(b)

Warm up the engine with normal idle speed.

(c)

Read the pre-catalytic oxygen sensor data.

Pre-Catalytic oxygen sensor standard value: 0.2-0.8 V

Is pre-catalytic oxygen sensor data is normal?

No

Refer to 

2.2.7.21

 

DTC P0130 P0131 P0132

P0133 P0134 P2195 P2196

Yes

Step 5

Observe the long-term fuel adjustment parameter.

(a)

Start the vehicle.

(b)

Warm up the engine.

(c)

Observe the long-term fuel adjustment parameter.

Is the long-term fuel adjustment parameter normal?

Yes

System normal.

No

Step 6

Check engine and its components.

(a)

Turn the ignition switch to "OFF" position.

(b)

Check the vacuum hose crack, kink or connections.

(c)

Check the intake manifold, throttle body and fuel injector
vacuum leakage.

(d)

Check the crankshaft ventilation system leakage.

(e)

Check fuel contamination.

(f)

Check the fuel system working at air-fuel ratio too lean.

(g)

Check injector nozzle spray fuel too lean.

(h)

Check the fuel system working at air-fuel ratio too rich.

(i)

Check injector spray fuel too rich.

(j)

Check intake manifold collapse or obstruction.

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Control System JL4G18-D

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(k)

Check whether there is excessive fuel in the crankcase.

(l)

Check evaporative emission control systems working
condition.

(m) Check other fault lights in I/P working condition.
Is engine System normal?

Yes

System normal

No

Step 7

Repair engine and its components.

Next

Step 8

System normal.

5. Repair Instructions:

Replace fuel injectors. Refer to 

2.2.8.2

 

Fuel Injector Replacement

.

Replace Canister solenoid valve. Refer to 

2.4.7.3

 

Canister Solenoid Valve Replacement

.

2.2.7.24 DTC P0201 P0261 P0262

1. DTC Descriptor:

DTC

P0201

Cylinder No.1 Fuel Injection Control Circuit Open

DTC

P0261

Cylinder No.1 Fuel Injector Control Circuit Short to Ground

DTC

P0262

Cylinder No.1 Fuel Injector Control Circuit Short to Power Supply

Fuel injector operating voltage is provided by The Main Relay which is controlled by ECM. Battery voltage passes through the main
relay terminal No.3 to all fuel injector wiring harness connectors terminal No.1. ECM controls fuel injector ground circuit by ECM
harness  connector  EN01  terminal  No.50.  ECM  monitors  all  fuel  injector  driver  circuit  status,  if  ECM  detects  driving  circuit
corresponding voltage is incorrect, ECM will set up a fuel injector control circuit fault DTC code.

2. Conditions For Setting DTC and The Fault Location:

DTC Code

DTC Detection Strategy

Conditions For Setting The DTC

(Control Strategy)

Fault Locations

P0201
P0261
P0262

Hardware Circuit Checks

1. Circuit Open.

2. Circuit Short to Ground.

3. Circuit Short to Power Supply.

1. Sensor Circuit

2. Sensor

3. ECM

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