DTC    P0171    System Too Lean (Bank 1)

DTC    P0172    System Too Rich (Bank 1)

DTC    P0174    System Too Lean (Bank 2)

DTC    P0175    System Too Rich (Bank 2)

for Preparation Click here


DESCRIPTION

The fuel trim is related to the feedback compensation value, not to the basic injection time. The fuel trim consists of both the short-term and the long-term fuel trims.
The short-term fuel trim is fuel compensation that is used to constantly maintain the air-fuel ratio at stoichiometric levels. The signal from the Air-Fuel Ratio (A/F) sensor indicates whether the air-fuel ratio is rich or lean compared to the stoichiometric ratio. This triggers a reduction in the fuel injection volume if the air-fuel ratio is rich and an increase in the fuel injection volume if it is lean.
Factors such as individual engine differences, wear over time and changes in operating environment cause short-term fuel trim to vary from the central value. The long-term fuel trim, which controls overall fuel compensation, compensates for long-term deviations in the fuel trim from the central value caused by the short-term fuel trim compensation.
If both the short-term and long-term fuel trims are lean or rich beyond predetermined values, it is interpreted as a malfunction, and the ECM (Included in HV Control ECU) illuminates the MIL and sets a DTC.

DTC No.
DTC Detection Condition
Trouble Area
P0171
P0174
With warm engine and stable air-fuel ratio feedback, fuel trim considerably in error to lean side
(2 trip detection logic)
  1. Air induction system
  2. Injector blockage
  3. Mass Air Flow (MAF) meter
  4. Engine Coolant Temperature (ECT) sensor
  5. Fuel pressure
  6. Gas leakage from exhaust system
  7. Open or short in A/F sensor (bank 1, 2 sensor 1) circuit
  8. A/F sensor (bank 1, 2 sensor 1)
  9. A/F sensor heater (bank 1, 2 sensor 1)
  10. A/F HTR relay
  11. A/F sensor heater and A/F HTR relay circuits
  12. PCV valve and hose
  13. PCV hose connections
  14. HV Control ECU
P0172
P0175
With warm engine and stable air-fuel ratio feedback, fuel trim considerably in error to rich side
(2 trip detection logic)
  1. Injector leakage or blockage
  2. MAF meter
  3. ECT sensor
  4. Ignition system
  5. Fuel pressure
  6. Gas leakage from exhaust system
  7. Open or short in A/F sensor (bank 1, 2 sensor 1) circuit
  8. A/F sensor (bank 1, 2 sensor 1)
  9. A/F sensor heater (bank 1, 2 sensor 1)
  10. A/F HTR relay
  11. A/F sensor heater and A/F HTR relay circuits
  12. HV Control ECU

HINT:
  1. When DTC P0171 or P0174 is set, the actual air-fuel ratio is on the lean side. When DTC P0172 or P0175 is set, the actual air-fuel ratio is on the rich side.
  2. If the vehicle runs out of fuel, the air-fuel ratio is lean and DTC P0171 or P0174 may be set. The MIL is then illuminated.
  3. When the total of the short-term and long-term fuel trim values is within the malfunction threshold (and the engine coolant temperature is more than 75°C [167°F]), the system is functioning normally.


WIRING DIAGRAM

Refer to DTC P2195 (Click here).

INSPECTION PROCEDURE

HINT:
Intelligent tester only:
Malfunctioning ares can be identified by performing the A/F Control function provided in the Active Test. The A/F Control function can help to determine whether the Air-Fuel Ratio (A/F) sensor, Heated Oxygen (HO2) sensor and other potential trouble areas are malfunctioning.
The following instructions describe how to conduct the A/F Control operation using an intelligent tester.
  1. Connect the intelligent tester to the DLC3.
  2. Put the engine in inspection mode (Click here).
  3. Start the engine and turn the tester ON.
  4. Warm up the engine at engine speed of 2,500 rpm for approximately 90 seconds.
  5. On the tester, enter the following menus: Powertrain / Engine / Active Test / A/F Control.
  6. Perform the A/F Control operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume.)
  7. Monitor the output voltages of the A/F and HO2 sensors (AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2) displayed on the tester.

HINT:
  1. The A/F Control operation lowers the fuel injection volume by 12.5 % or increases the injection volume by 25 %.
  2. Each sensor reacts in accordance with increases and decreases in the fuel injection volume.


Standard:

Tester Display
(Sensor)
Injection Volume
Status
Voltage
AFS B1S1 or AFS B2S1
(A/F)
+25 %
Rich
Less than 3.0
AFS B1S1 or AFS B2S1
(A/F)
-12.5 %
Lean
More than 3.35
O2S B1S2 or O2S B2S2
(HO2)
+25 %
Rich
 More than 0.55
O2S B1S2 or O2S B2S2
(HO2)
-12.5 %
Lean
Less than 0.4

NOTICE:
The Air-Fuel Ratio (A/F) sensor has an output delay of a few seconds and the Heated Oxygen (HO2) sensor has a maximum output delay of approximately 20 seconds.


Case
A/F Sensor (Sensor 1)
Output Voltage
HO2 Sensor (Sensor 2)
Output Voltage
Main Suspected Trouble Area
1
Injection Volume
+25 %
-12.5 %
A103184
Injection Volume
+25 %
-12.5 %
A103184
-
Output Voltage
More than 3.35 V
Less than 3.0 V
A107708
Output Voltage
More than 0.55 V
Less than 0.4 V
A103186
2
Injection Volume
+25 %
-12.5 %
A103184
Injection Volume
+25 %
-12.5 %
A103184
  1. A/F sensor
  2. A/F sensor heater
    A/F sensor circuit
Output Voltage
Almost
no reaction
A103185
Output Voltage
More than 0.55 V
Less than 0.4 V
A103186
3
Injection Volume
+25 %
-12.5 %
A103184
Injection Volume
+25 %
-12.5 %
A103184
  1. HO2 sensor
  2. HO2 sensor heater
  3. HO2 sensor circuit
Output Voltage
More than 3.35 V
Less than 3.0 V
A107708
Output Voltage
Almost
no reaction
A103185
4
Injection volume
+25 %
-12.5 %
A103184
Injection Volume
+25 %
-12.5 %
A103184
  1. Injector
  2. Fuel pressure
  3. Gas leakage from exhaust system
    (Air-fuel ratio extremely lean or rich)
Output Voltage
Almost
no reaction
A103185
Output Voltage
Almost
no reaction
A103185
Following the A/F Control procedure enables technicians to check and graph the voltage outputs of both the A/F and HO2 sensors.

HINT:
  1. Read freeze frame data using the intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was LEAN or RICH, and other data from the time the malfunction occurred.
  2. A low A/F sensor voltage could be caused by a rich air-fuel mixture. Check for conditions that would cause the engine to run rich.
  3. A high A/F sensor voltage could be caused by a rich air-fuel mixture. Check for conditions that would cause the engine to run lean.

1.CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0171, P0172, P0174 OR P0175)

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch ON and turn the tester ON.

  1. Enter the following menus: Powertrain / Engine / DTC.

  1. Read DTCs.

    Result:

    Display (DTC output)
    		Proceed to
    P0171, P0172, P0174 or P0175
    		A
    P0171, P0172, P0174 or P0175 and other DTCs
    		B

    HINT:
    If any DTCs other than P0171, P0172, P0174 or P0175 are output, troubleshoot those DTCs first.



B
GO TO DTC CHART
A


2.CHECK PCV HOSE

OK:
PCV hose is connected correctly and is not damaged.



NG
REPAIR OR REPLACE PCV HOSE
OK


3.CHECK AIR INDUCTION SYSTEM

  1. Check the air induction system for vacuum leakage.

    OK:
    No leakage from air induction system.



NG
REPAIR OR REPLACE AIR INDUCTION SYSTEM
OK


4.PERFORM ACTIVE TEST USING INTELLIGENT TESTER (A/F CONTROL)

  1. Connect the intelligent tester to the DLC3.

  1. Put the engine in inspection mode (Click here).

  1. Start the engine and turn the tester ON.

  1. Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.

  1. On the tester, enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor.

  1. Perform the A/F Control operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).

  1. Monitor the outputs voltages of A/F and HO2 sensors (AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2) displayed on the tester.

    HINT:
    1. The A/F Control operation lowers the fuel injection volume by 12.5 % or increases the injection volume by 25 %.
    2. Each sensor reacts in accordance with increases and decreases in the fuel injection volume.


    Standard:

    Tester Display
    (Sensor)
    		Injection Volume
    		Status
    		Voltage
    AFS B1S1 or AFS B2S1
    (A/F)
    		+25 %
    		Rich
    		Less than 3.0
    AFS B1S1 or AFS B2S1
    (A/F)
    		-12.5 %
    		Lean
    		More than 3.35
    O2S B1S2 or O2S B2S2
    (HO2)
    		+25 %
    		Rich
    		 More than 0.55
    O2S B1S2 or O2S B2S2
    (HO2)
    		-12.5 %
    		Lean
    		Less than 0.4


    Result:

    Status
    AFS B1S1
    or
    AFS B2S1
    		Status
    O2S B1S2
    or
    O2S B2S2
    		A/F Condition and
    A/F Sensor Condition
    		Misfire
    		Suspected Trouble Area
    		Proceed to
    Lean/Rich
    		Lean/Rich
    		Normal
    		-
    		-
    		C
    Lean
    		Lean
    		Actual air-fuel ratio lean
    		May occur
    1. PCV valve and hose
    2. PCV hose connections
    3. Injector blockage
    4. Gas leakage from exhaust system
    5. Air induction system
    6. Fuel pressure
    7. Mass Air Flow (MAF) meter
    8. Engine Coolant Temperature (ECT) sensor
    		A
    Rich
    		Rich
    		Actual air-fuel ratio rich
    		-
    1. Injector blockage or blockage
    2. Gas leakage from exhaust system
    3. Ignition system
    4. Fuel pressure
    5. MAF meter
    6. ECT sensor
    		A
    Lean
    		Lean/Rich
    		A/F sensor malfunction
    		-
    1. A/F sensor
    		B
    Rich
    		Lean/Rich
    		A/F sensor malfunction
    		-
    1. A/F sensor
    		B

    Lean: During A/F Control, the A/F sensor output voltage (AFS) is consistently more than 3.35 V, and the HO2 sensor output voltage (O2S) is consistently less than 0.4 V.
    Rich: During A/F Control, the AFS is consistently less than 3.0 V, and the O2S is consistently more than 0.55 V.



B
Go to step 10

C
Go to step 14
A


5.READ VALUE USING INTELLIGENT TESTER (COOLANT TEMP)

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch ON and turn the tester ON.

  1. Enter the following menus: Powertrain / Engine / Data List / Coolant Temp.

  1. Read the Coolant Temp twice, when the engine is both cold and warmed up.

    Standard:
    With cold engine:
    Same as ambient air temperature.
    With warm engine:
    Between 75 and 95°C (167 and 203°F)



NG
REPLACE ENGINE COOLANT TEMPERATURE SENSOR
OK


6.READ VALUE USING INTELLIGENT TESTER (MAF)

  1. Connect the intelligent tester to the DLC3.

  1. Turn the tester ON.

  1. Enter the following menus: Powertrain / Engine / Data List / MAF.

  1. Read the MAF with the engine stopped.

    Standard:
    MAF while engine stopped:
    0.54 g/s or less

  1. Put the engine in inspection mode (Click here).

  1. Enter the following menus: Powertrain / Engine / Data List / MAF and Coolant Temp.

  1. Allow the engine to idle until the Coolant Temp reaches 75°C (167°F) or more.

  1. Read the MAF with the engine in an idling condition and at an engine speed of 2,500 rpm.

    Standard:
    MAF while engine idling:
    Between 2.0 g/s and 4.3 g/s (shift position: N, A/C: OFF).
    MAF at an engine speed of 2,500 rpm:
    Between 12.1 g/s and 18.2 g/s (shift position: N, A/C: OFF).



NG
REPLACE MASS AIR FLOW METER
OK


7.CHECK FUEL PRESSURE

  1. Check the fuel pressure (Click here).

    Standard:
    304 to 343 kPa (3.1 to 3.5 kgf/cm2, 44.1 to 49.7 psi)



NG
CHECK AND REPLACE FUEL PUMP, PRESSURE REGULATOR, FUEL PIPE LINE AND FILTER
OK


8.CHECK FOR EXHAUST GAS LEAKAGE

OK:
No gas leakage.



NG
REPAIR OR REPLACE EXHAUST SYSTEM
OK


9.CHECK FOR SPARKS AND IGNITION

HINT:
If the spark plugs or ignition system malfunctions, engine misfire may occur. The misfire count can be read using an intelligent tester. Enter the following menus: Powertrain / Engine / Data List / Cylinder #1 (to #6) Misfire Rate.



NG
REPAIR OR REPLACE IGNITION SYSTEM
OK


10.INSPECT FUEL INJECTOR ASSEMBLY (INJECTION AND VOLUME)

HINT:
If the injectors malfunction, engine misfire may occur. The misfire count can be read using the intelligent tester. Enter the following menus: Powertrain / Engine / Data List / Cylinder #1 (to #6) Misfire Rate.



NG
REPLACE FUEL INJECTOR ASSEMBLY
OK


11.INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)


    A052607E13

  1. Disconnect the A4 or A5 A/F sensor connector.

  1. Measure the resistance between the terminals of the A/F sensor connector.

    Standard resistance:
    Tester Connection
    		Specified Condition
    HA1A, HA2A - +B
    		1.8 Ω to 3.4 Ω at 20°C (68°F)
    HA1A, HA2A - A1A-, A2A-
    		10 kΩ or higher

  1. Reconnect the A/F sensor connector.



NG
REPLACE AIR FUEL RATIO SENSOR
OK


12.INSPECT A/F RELAY


    B016200E02

  1. Remove the A/F relay from the engine room No. 2 relay block.

  1. Measure the A/F relay resistance.

    Standard resistance:
    Tester Connection
    		Specified Condition
    3 - 5
    		10 kΩ or higher
    3 - 5
    		Below 1 Ω
    (when battery voltage applied to terminals 1 and 2)

  1. Reinstall the A/F relay.



NG
REPLACE A/F RELAY
OK


13.CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM)


    A110905E03

  1. Disconnect the A4 and A5 A/F sensor connector.

  1. Turn the ignition switch ON.

  1. Measure the voltage between the +B terminal of the A/F sensor connector and body ground.

    Standard voltage:
    Tester Connection
    		Specified Condition
    +B - Body ground
    		9 to 14 V

  1. Turn the engine switch off.

  1. Disconnect the H33 HV Control ECU connector.

  1. Measure the resistance between the terminals of the A/F sensor and HV Control ECU.

    Standard resistance (Check for open):
    Tester Connection
    		Specified Condition
    HA1A ( A5-1) - HA1A (H33-4)
    		Below 1 Ω
    A1A+ (A5-3) - A1A+ (H33-22)
    		Below 1 Ω
    A1A- (A5-4) - A1A- (H33-30)
    		Below 1 Ω
    HA2A (A4-1) - HA2A (H33-3)
    		Below 1 Ω
    A2A+ (A4-3) - A2A+ (H33-23)
    		Below 1 Ω
    A2A- (A4-4) - A2A- (H33-31)
    		Below 1 Ω

    Standard resistance (Check for short):
    Tester Connection
    		Specified Condition
    HA1A ( A5-1) or HA1A (H33-4) - Body ground
    		10 kΩ or higher
    A1A+ (A5-3) or A1A+ (H33-22) - Body ground
    		10 kΩ or higher
    A1A- (A5-4) or A1A- (H33-30) - Body ground
    		10 kΩ or higher
    HA2A (A4-1) or HA2A (H33-3) - Body ground
    		10 kΩ or higher
    A2A+ (A4-3) or A2A+ (H33-23) - Body ground
    		10 kΩ or higher
    A2A- (A4-4) or A2A- (H33-31) - Body ground
    		10 kΩ or higher

  1. Reconnect the HV Control ECU connector.



  1. Reconnect the A/F sensor connector.


    A103833E12



NG
REPAIR OR REPLACE HARNESS AND CONNECTOR
OK


14.REPLACE AIR FUEL RATIO SENSOR

NEXT


15.PERFORM CONFIRMATION DRIVING PATTERN


  1. Connect the intelligent tester to the DLC3.


    A079199E08

  1. Turn the ignition switch ON and turn the tester ON.

  1. Clear DTCs (Click here).

  1. Switch the ECM from normal mode to check mode using the tester (Click here).

  1. Start the engine and warm it up with all the accessories switched OFF.

  1. Drive the vehicle at between 47 mph and 75 mph (75 km/h and 120 km/h) and at an engine speed of between 1,400 rpm and 3,200 rpm for 3 to 5 minutes.

    HINT:
    If the system is still malfunctioning, the MIL will be illuminated during step (f).

    NOTICE:
    If the conditions in this test are not strictly followed, no malfunction will be detected.


NEXT


16.CHECK WHETHER DTC OUTPUT RECURS (DTC P0171, P0172, P0174 OR P0175)

  1. On the intelligent tester, enter the following menus: Powertrain / Engine / DTC.

  1. Read DTCS.

    Result:

    Display (DTC output)
    		Proceed to
    No output
    		A
    P0171, P0172, P0174 or P0175
    		B



B
Go to step 5
A

END