Dtc P0171 System Too Lean (Bank 1)

Engine. Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35
3Zr-Fae Engine Control System. Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35

DESCRIPTION

MONITOR DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0171 OR P0172)

PERFORM ACTIVE TEST USING INTELLIGENT TESTER (AIR FUEL RATIO CONTROL)

CONFIRM IF VEHICLE HAS RUN OUT OF FUEL IN PAST

PERFORM CONFIRMATION DRIVING PATTERN

CHECK WHETHER DTC OUTPUT RECURS (DTC P0171 OR P0172)

CHECK FOR EXHAUST GAS LEAK

CHECK FUEL PRESSURE

INSPECT INJECTOR ASSEMBLY (INJECTION VOLUME)

INSPECT MASS AIR FLOW METER

READ VALUE USING INTELLIGENT TESTER (COOLANT TEMP)

CHECK PCV HOSE CONNECTIONS

CHECK INTAKE SYSTEM

CHECK IGNITION SYSTEM

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

CHECK AIR FUEL RATIO SENSOR (POWER SOURCE)

CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM)

REPLACE AIR FUEL RATIO SENSOR

PERFORM CONFIRMATION DRIVING PATTERN

CHECK WHETHER DTC OUTPUT RECURS (DTC P0171 OR P0172)

CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - INTEGRATION RELAY)

CHECK FUEL LINE

DTC P0171 System Too Lean (Bank 1)

DTC P0172 System Too Rich (Bank 1)


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 trim.
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 sensor (sensor 1) 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 change 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 illuminates the MIL and stores a DTC.

DTC No.
DTC Detection Condition
Trouble Area
P0171
With a warm engine and stable air fuel ratio feedback, fuel trim is too lean (2 trip detection logic).
  1. Intake system
  2. Fuel pressure
  3. Injector blockage
  4. Mass air flow meter
  5. Engine coolant temperature sensor
  6. Gas leakage from exhaust system
  7. Open or short in heated oxygen sensor (sensor 2) circuit
  8. Air fuel ratio sensor (sensor 1)
  9. Air fuel ratio sensor heater (sensor 1)
  10. Air fuel ratio sensor heater circuit
  11. PCV hose connections
  12. PCV valve and hose
  13. ECM
P0172
With a warm engine and stable air fuel ratio feedback, fuel trim is too rich (2 trip detection logic).
  1. Injector leakage or blockage
  2. Fuel pressure
  3. Mass air flow meter
  4. Engine coolant temperature sensor
  5. Ignition system
  6. Gas leakage from exhaust system
  7. Open or short in heated oxygen sensor (sensor 2) circuit
  8. Air fuel ratio sensor (sensor 1)
  9. Air fuel ratio sensor heater (sensor 1)
  10. Air fuel ratio sensor heater circuit
  11. Ignition system
  12. ECM
HINT:
  1. When DTC P0171 is stored, the actual air fuel ratio is too lean. When DTC P0172 is stored, the actual air fuel ratio is too rich.
  2. If the vehicle runs out of fuel, the air fuel ratio is lean and DTC P0171 may be stored. The MIL is then illuminated.
  3. When the total of the short-term and long-term fuel trim values is within 20% of the central value (and the engine coolant temperature is higher than 75°C [167°F]), the system is functioning normally.

MONITOR DESCRIPTION

Under closed-loop fuel control, fuel injection volumes that deviate from those estimated by the ECM cause changes in the long-term fuel trim compensation value. The long-term fuel trim is adjusted when there are persistent deviations in the short-term fuel trim values. Deviations from the fuel injection volumes estimated by the ECM also affect the average fuel trim learned value, which is a combination of the average short-term fuel trim (fuel feedback compensation value) and the average long-term fuel trim (learned value of the air fuel ratio). If the average fuel trim learned value exceeds the malfunction threshold, the ECM interprets this as a fault in the fuel system and stores a DTC.
Example:
If the average fuel trim learned value is +35% or more or -35% or less, the ECM interprets this as a fuel system malfunction.

Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35.3Zr-Fae Engine Control System.Sfi System. Dtc P0171 System Too Lean (Bank 1)


WIRING DIAGRAM

Refer to DTC P2195 (RAV4_ACA30 RM000000WC40NNX_07.html).

INSPECTION PROCEDURE

NOTICE:
Inspect the fuses for circuits related to this system before performing the following inspection procedure.
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 moving or stationary, 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 air fuel ratio 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 air fuel ratio sensor voltage could be caused by a lean 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 OR P0172)

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the tester on.

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

  1. Read the DTCs.


Result
Result
Proceed to
DTC P0171 or P0172 is output
A
DTC P0171 or P0172 and other DTCs are output
B
HINT:
If any DTCs other than P0171 or P0172 are output, troubleshoot those DTCs first.


B
GO TO DTC CHART (RAV4_ACA30 RM000000PDF0FMX.html)
A


2.PERFORM ACTIVE TEST USING INTELLIGENT TESTER (AIR FUEL RATIO CONTROL)

  1. Connect the intelligent tester to the DLC3.

  1. Start the engine.

  1. Turn the tester on.

  1. Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.

  1. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.

  1. Perform the "Control the Injection Volume for A/F Sensor" operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume).

  1. Monitor the output voltages of the air fuel ratio sensor (sensor 1) and heated oxygen sensor (sensor 2) (AFS Voltage B1 S1 and O2S B1 S2) displayed on the tester.

Result:
The air fuel ratio sensor (sensor 1) reacts in accordance with increases and decreases in the fuel injection volume:
+25% = Rich output:
Higher than 3.4 V
-12.5% = Lean output:
Below 3.1 V
NOTICE:
The air fuel ratio sensor (sensor 1) has an output delay of a few seconds and the heated oxygen sensor (sensor 2) 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
Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35
Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35
Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35
Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35
-
2
Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35
Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35
Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35
Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35
  1. A/F sensor
  2. A/F sensor heater
  3. A/F sensor circuit
3
Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35
Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35
Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35
Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35
  1. Injector
  2. Fuel pressure
  3. Gas leak from exhaust system (Air fuel ratio extremely rich or lean)
  1. Following the "Control the Injection Volume for A/F Sensor" procedure enables technicians to check and graph the voltage outputs of both the air fuel ratio sensor (sensor 1) and heated oxygen sensor (sensor 2).
  2. To display the graph, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / AFS Voltage B1 S1 and O2S B1 S2.

Result
Result
Proceed to
Case 1
A
Case 2
B
Case 3
C


B
Go to step 14

C
Go to step 6
A


3.CONFIRM IF VEHICLE HAS RUN OUT OF FUEL IN PAST

  1. Has the vehicle run out of fuel in the past?



NO
Go to step 6
YES


4.PERFORM CONFIRMATION DRIVING PATTERN

Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35.3Zr-Fae Engine Control System.Sfi System. Dtc P0171 System Too Lean (Bank 1)

  1. Connect the intelligent tester to the DLC3 (Procedure "A").

  1. Turn the ignition switch to ON (Procedure "B").

  1. Turn the tester on (Procedure "C").

  1. Clear the DTCs (RAV4_ACA30 RM000000PDK0WCX.html) (Procedure "D").

  1. Switch the ECM from normal mode to check mode (RAV4_ACA30 RM000000PDL0A2X.html) (Procedure "E").

  1. Start the engine (Procedure "F").

  1. Allow the engine to idle until the engine coolant temperature reaches 40°C (104°F) (Procedure "G").

  1. Drive the vehicle at a vehicle speed of more than 40 km/h (25 mph) for 35 seconds or more (Procedure "H").

  1. Allow the engine to idle for 40 seconds or more (Procedure "I").

  1. Repeat procedures "G" through "I" described above at least 3 times (Procedure "J").

  1. Allow the engine to idle for 40 seconds or more (Procedure "K").

    HINT:
    The MIL is illuminated during procedure "K" if a malfunction still exists.
    NOTICE:
    If the conditions in this test are not strictly followed, malfunctions may not be detected.

NEXT


5.CHECK WHETHER DTC OUTPUT RECURS (DTC P0171 OR P0172)

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the tester on.

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

  1. Read the DTCs.

    Result
    Result
    		Proceed to
    DTC P0171 or P0172 is output
    		A
    DTC is not output
    		B


B
SYSTEM IS OK
A


6.CHECK FOR EXHAUST GAS LEAK

  1. Check for exhaust gas leakage.

    OK:
    No gas leakage.


NG
REPAIR OR REPLACE EXHAUST SYSTEM
OK


7.CHECK FUEL PRESSURE

  1. Check the fuel pressure (RAV4_ACA30 RM000001IQZ02QX_01_0002.html).



NG
Go to step 21
OK


8.INSPECT INJECTOR ASSEMBLY (INJECTION VOLUME)

  1. Check the injection volume (RAV4_ACA30 RM000001EDQ01NX.html).



NG
REPLACE FUEL INJECTOR ASSEMBLY (RAV4_ACA30 RM000001EDS01DX.html)
OK


9.INSPECT MASS AIR FLOW METER

  1. Inspect the mass air flow meter (RAV4_ACA30 RM000000Q2D046X.html).



NG
REPLACE MASS AIR FLOW METER (RAV4_ACA30 RM000002WQT00SX.html)
OK


10.READ VALUE USING INTELLIGENT TESTER (COOLANT TEMP)

  1. Connect the intelligent tester to the DLC3.

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

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

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

    Standard temperature:
    With cold engine: Same as ambient air temperature.
    With warm engine: Between 75°C and 100°C (167°F and 212°F).


NG
REPLACE ENGINE COOLANT TEMPERATURE SENSOR (RAV4_ACA30 RM000002WSG02VX.html)
OK


11.CHECK PCV HOSE CONNECTIONS

  1. Check the PCV hose connections (RAV4_ACA30 RM0000012OO02QX_01_0003.html).

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


NG
REPAIR OR REPLACE PCV HOSE
OK


12.CHECK INTAKE SYSTEM

  1. Check the intake system for vacuum leakage (RAV4_ACA30 RM00000341000BX.html).

    OK:
    No leakage from intake system.


NG
REPAIR OR REPLACE INTAKE SYSTEM
OK


13.CHECK IGNITION SYSTEM

  1. Inspect the ignition system (RAV4_ACA30 RM000001EFG02EX.html).



NG
REPAIR OR REPLACE IGNITION SYSTEM
OK


14.INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)


    Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35.3Zr-Fae Engine Control System.Sfi System. Dtc P0171 System Too Lean (Bank 1)

  1. Disconnect the air fuel ratio sensor connector.

  1. Measure the resistance according to the value(s) in the table below.

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    1 (HA1A) - 2 (+B)
    		20°C (68°F)
    		1.8 to 3.4 Ω
    1 (HA1A) - 4 (A1A-)
    		Always
    		10 kΩ or higher
    Text in Illustration
    *1
    		Component without harness connected
    (Air Fuel Ratio Sensor)

  1. Reconnect the air fuel ratio sensor connector.



NG
REPLACE AIR FUEL RATIO SENSOR (RAV4_ACA30 RM000002WUR027X.html)
OK


15.CHECK AIR FUEL RATIO SENSOR (POWER SOURCE)


    Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35.3Zr-Fae Engine Control System.Sfi System. Dtc P0171 System Too Lean (Bank 1)

  1. Disconnect the air fuel ratio sensor connector.

  1. Measure the voltage according to the value(s) in the table below.

    Standard Voltage:
    Tester Connection
    		Switch Condition
    		Specified Condition
    B113-2 (+B) - Body ground
    		Ignition switch ON
    		11 to 14 V
    Text in Illustration
    *1
    		Front view of wire harness connector
    (to Air Fuel Ratio Sensor)

  1. Reconnect the air fuel ratio sensor connector.



NG
Go to step 20
OK


16.CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM)


    Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35.3Zr-Fae Engine Control System.Sfi System. Dtc P0171 System Too Lean (Bank 1)

  1. Disconnect the air fuel ratio sensor connector.

  1. Disconnect the ECM connector.

  1. Measure the resistance according to the value(s) in the table below.

    Standard Resistance (Check for Open):
    Tester Connection
    		Condition
    		Specified Condition
    B113-1 (HA1A) - B32-104 (HA1A)
    		Always
    		Below 1 Ω
    B113-3 (A1A+) - B32-103 (A1A+)
    		Always
    		Below 1 Ω
    B113-4 (A1A-) - B32-126 (A1A-)
    		Always
    		Below 1 Ω
    Standard Resistance (Check for Short):
    Tester Connection
    		Condition
    		Specified Condition
    B113-1 (HA1A) or B32-104 (HA1A) - Body ground
    		Always
    		10 kΩ or higher
    B113-3 (A1A+) or B32-103 (A1A+) - Body ground
    		Always
    		10 kΩ or higher
    B113-4 (A1A-) or B32-126 (A1A-) - Body ground
    		Always
    		10 kΩ or higher
    Text in Illustration
    *1
    		Front view of wire harness connector
    (to Air Fuel Ratio Sensor)
    *2
    		Front view of wire harness connector
    (to ECM)

  1. Reconnect the ECM connector.



  1. Reconnect the air fuel ratio sensor connector.


    Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35.3Zr-Fae Engine Control System.Sfi System. Dtc P0171 System Too Lean (Bank 1)



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR (AIR FUEL RATIO SENSOR - ECM)
OK


17.REPLACE AIR FUEL RATIO SENSOR

  1. Replace the air fuel ratio sensor (RAV4_ACA30 RM000002WUR027X.html).


NEXT


18.PERFORM CONFIRMATION DRIVING PATTERN

Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35.3Zr-Fae Engine Control System.Sfi System. Dtc P0171 System Too Lean (Bank 1)

  1. Connect the intelligent tester to the DLC3 (Procedure "A").

  1. Turn the ignition switch to ON (Procedure "B").

  1. Turn the tester on (Procedure "C").

  1. Clear the DTCs (RAV4_ACA30 RM000000PDK0WCX.html) (Procedure "D").

  1. Switch the ECM from normal mode to check mode (RAV4_ACA30 RM000000PDL0A2X.html) (Procedure "E").

  1. Start the engine (Procedure "F").

  1. Allow the engine to idle until the engine coolant temperature reaches 40°C (104°F) (Procedure "G").

  1. Drive the vehicle at a vehicle speed of more than 40 km/h (25 mph) for 35 seconds or more (Procedure "H").

  1. Allow the engine to idle for 40 seconds or more (Procedure "I").

  1. Repeat procedures "G" through "I" described above at least 3 times (Procedure "J").

  1. Allow the engine to idle for 40 seconds or more (Procedure "K").

    HINT:
    The MIL is illuminated during procedure "K" if a malfunction still exists.
    NOTICE:
    If the conditions in this test are not strictly followed, malfunctions may not be detected.

NEXT


19.CHECK WHETHER DTC OUTPUT RECURS (DTC P0171 OR P0172)

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the tester on.

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

  1. Read the DTCs.


Result
Result
Proceed to
DTC is not output
A
DTC P0171 or P0172 is output
B


B
REPLACE ECM (RAV4_ACA30 RM0000017UO01KX.html)
A

END

20.CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - INTEGRATION RELAY)


    Toyota Rav4. Aca30, 33, 38 Gsa33 Zsa30, 35.3Zr-Fae Engine Control System.Sfi System. Dtc P0171 System Too Lean (Bank 1)

  1. Disconnect the air fuel ratio sensor connector.

  1. Remove the integration relay (EFI MAIN relay) from the engine room No. 1 relay block.

  1. Disconnect the integration relay connector.

  1. Measure the resistance according to the value(s) in the table below.

    Standard Resistance (Check for Open):
    Tester Connection
    		Condition
    		Specified Condition
    B113-2 (+B) - 1A-4
    		Always
    		Below 1 Ω
    Standard Resistance (Check for Short):
    Tester Connection
    		Condition
    		Specified Condition
    B113-2 (+B) or 1A-4 - Body ground
    		Always
    		10 kΩ or higher
    Text in Illustration
    *1
    		Front view of wire harness connector
    (to Air Fuel Ratio Sensor)
    *2
    		Front view of wire harness connector
    (to Integration Relay)
    *3
    		Engine Room No. 1 Relay Block

  1. Reconnect the air fuel ratio sensor connector.

  1. Reconnect the integration relay connector.

  1. Reinstall the integration relay.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR (AIR FUEL RATIO SENSOR - INTEGRATION RELAY)
OK

GO TO ECM POWER SOURCE CIRCUIT (RAV4_ACA30 RM00000276902PX.html)

21.CHECK FUEL LINE

  1. Check the fuel lines for leaks or blockage (RAV4_ACA30 RM000001EEZ00XX.html).

    OK:
    No leaks or blockage.


NG
REPAIR OR REPLACE FUEL LINE
OK

REPLACE FUEL PUMP (RAV4_ACA30 RM0000017RJ032X.html)