Toyota Venza manuals

Toyota Venza: System Too Lean (Bank 1) (P0171,P0172)

Toyota Venza Service Manual / 1ar-fe Engine Control / Sfi System / System Too Lean (Bank 1) (P0171,P0172)

DESCRIPTION

The fuel trim is related to the feedback compensation value, not to the basic injection duration. The fuel trim consists of both the short-term and 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 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 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 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, the fuel trim is considerably in error to the lean side (2 trip detection logic).

  • Intake system
  • Injector blockage
  • Mass air flow meter
  • Engine coolant temperature sensor
  • Fuel pressure
  • Gas leak from exhaust system
  • Open or short in air fuel ratio sensor (bank 1 sensor 1) circuit
  • Air fuel ratio sensor (bank 1 sensor 1)
  • PCV valve and hose
  • PCV hose connections
  • Wire harness or connector
  • ECM

P0172

With a warm engine and stable air fuel ratio feedback, the fuel trim is considerably in error to the rich side (2 trip detection logic).

  • Intake system
  • Injector leak or blockage
  • Mass air flow meter
  • Engine coolant temperature sensor
  • Ignition system
  • Fuel pressure
  • Gas leak from exhaust system
  • Open or short in air fuel ratio sensor (bank 1 sensor 1) circuit
  • Air fuel ratio sensor (bank 1 sensor 1)
  • Wire harness or connector
  • ECM

HINT:

  • When DTC P0171 is stored, the actual air fuel ratio is on the lean side. When DTC P0172 is stored, the actual air fuel ratio is on the rich side.
  • If the vehicle runs out of fuel, the air fuel ratio is lean and DTC P0171 may be stored. The MIL is then illuminated.
  • When the total of the short-term and long-term fuel trim values is within the malfunction threshold (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 thresholds, the ECM interprets this as a fault in the fuel system and stores a DTC.

Example:

The average fuel trim learned value is +35% or more, or -35% or less, the ECM interprets this as a fuel system malfunction.


MONITOR STRATEGY

Related DTCs

P0171: Fuel trim lean

P0172: Fuel trim rich

Required Sensors/Components (Main)

Fuel system

Required Sensors/Components (Related)

Air fuel ratio sensor

Mass air flow meter

Crankshaft position sensor

Frequency of Operation

Continuous

Duration

Within 10 seconds

MIL Operation

2 driving cycles

Sequence of Operation

None

TYPICAL ENABLING CONDITIONS

Fuel-trim:

Monitor runs whenever following DTCs not stored

P0010 (Camshaft Timing Oil Control Valve)

P0011 (VVT System - Advance)

P0012 (VVT System - Retard)

P0016 (VVT System - Misalignment)

P0013 (Exhaust Camshaft Timing Oil Control Valve)

P0014 (Exhaust VVT System - Advance)

P0015 (Exhaust VVT System - Retard)

P0017 (Exhaust VVT System - Misalignment)

P0031, P0032, P101D (Air Fuel Ratio Sensor Heater)

P0102, P0103 (Mass Air Flow Meter)

P0115, P0117, P0118 (Engine Coolant Temperature Sensor)

P0125 (Insufficient Coolant Temperature for Closed Loop Fuel Control)

P0120, P0121, P0122, P0123, P0220, P0222, P0223, P2135 (Throttle Position Sensor)

P0335 (Crankshaft Position Sensor)

P0340, P0342, P0343 (Camshaft Position Sensor)

P0365, P0367, P0368 (Exhaust Camshaft Position Sensor)

P0351 - P0354 (Igniter)

P0500 (Vehicle Speed Sensor)

P219A, P219C, P219D, P219E, P219F (Air Fuel Ratio Imbalance)

Fuel system status

Closed loop

Battery voltage

11 V or higher

Either of following conditions 1 or 2 met

-

1. Engine speed

Less than 800 rpm

2. Engine load

16.25% or more

Catalyst monitor

Not executed

TYPICAL MALFUNCTION THRESHOLDS

Fuel-trim:

Purge-cut

Executing

Either of following conditions 1 or 2 met

-

1. Average between short-term fuel trim and long-term fuel trim

35% or more (varies with engine coolant temperature)

2. Average between short-term fuel trim and long-term fuel trim

-35% or less (varies with engine coolant temperature)

CONFIRMATION DRIVING PATTERN


  1. Connect the Techstream to the DLC3.
  2. Turn the ignition switch to ON and turn the Techstream on.
  3. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure) (See page ).

  4. Turn the ignition switch off and wait for at least 30 seconds.
  5. Turn the ignition switch to ON and turn the Techstream on [A].
  6. Start the engine and warm it up (until the engine coolant temperature is 75°C (167°F) or higher) with all the accessories switched off [B].
  7. With the engine warmed up, idle the engine for 2 minutes or more [C].
  8. Drive the vehicle at between 60 and 135 km/h (37 and 84 mph) for 5 minutes or more [D].

    CAUTION:

    When performing the confirmation driving pattern, obey all speed limits and traffic laws.

  9. If the test result is N/A, enter the following menus: Powertrain / Engine / Trouble Codes [E].
  10. Read Pending DTCs.

    HINT:

    If a pending DTC is output, the system is malfunctioning.

  11. If no pending DTC is output, perform a universal trip and check for permanent DTCs (See page ).

    HINT:

    • If a permanent DTC is output, the system is malfunctioning.
    • If no permanent DTC is output, the system is normal.

WIRING DIAGRAM

Refer to DTC P0102 (See page ).


Refer to DTC P2195 (See page ).


CAUTION / NOTICE / HINT

NOTICE:

Inspect the fuses for circuits related to this system before performing the following inspection procedure.

HINT:

  • Sensor 1 refers to the sensor closest to the engine assembly.
  • Sensor 2 refers to the sensor farthest away from the engine assembly.
  • Read freeze frame data using the Techstream. Freeze frame data records the engine condition when malfunctions are detected. 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.

PROCEDURE

1.

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

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine / Trouble Codes.

(e) Read the DTCs.

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


A

2.

CHECK PCV HOSE CONNECTIONS

(a) Check the PCV hose connections (See page ).


OK:

PCV hose is connected correctly and is not damaged.


NG

REPAIR OR REPLACE PCV HOSE


OK

3.

CHECK INTAKE SYSTEM

(a) Check the intake system for vacuum leaks (See page ).


OK:

No leakage from intake system.

HINT:

  • If a malfunction is detected while the brake pedal is being depressed, vacuum leaks in the brake booster assembly are suspected. Inspect the brake booster assembly.
  • Perform "Inspection After Repair" after repairing or replacing the intake system (See page ).


NG

REPAIR OR REPLACE INTAKE SYSTEM


OK

4.

PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE INJECTION VOLUME)

(a) Connect the Techstream to the DLC3.

(b) Start the engine.

(c) Turn the Techstream on.

(d) Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.

(e) Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume / AFS Voltage B1S1 and O2S B1S2.

(f) Perform the Control the Injection Volume operation with the engine idling.

(g) Monitor the voltage outputs of the air fuel ratio sensor and the heated oxygen sensor (AFS Voltage B1S1 and O2S B1S2) displayed on the Techstream.

HINT:

  • Change the fuel injection volume within the range of -12% and +12%. The injection volume can be changed in fine gradations.
  • The air fuel ratio sensor has an output delay of a few seconds and the heated oxygen sensor has a maximum output delay of approximately 20 seconds.
  • If the sensor output voltage does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.

Standard:

Techstream Display

(Sensor)

Injection Volume

Status

Voltage

AFS Voltage B1S1

(Air fuel ratio)

+12%

Rich

Below 3.1 V

-12%

Lean

Higher than 3.4 V

O2S B1S2

(Heated oxygen)

+12%

Rich

Higher than 0.55 V

-12%

Lean

Below 0.4 V

Status

AFS Voltage B1S1

Status

O2S B1S2

Air Fuel Ratio Condition and

Air Fuel Ratio Sensor Condition

Suspected Trouble Area

Proceed to

Lean

Lean

Actual air fuel ratio lean

  • PCV valve and hose
  • PCV hose connections
  • Fuel injector blockage
  • Gas leak from exhaust system
  • Intake system
  • Fuel pressure
  • Mass air flow meter
  • Engine coolant temperature sensor

A

Rich

Rich

Actual air fuel ratio rich

  • Fuel injector leak or blockage
  • Gas leak from exhaust system
  • Ignition system
  • Fuel pressure
  • Mass air flow meter
  • Engine coolant temperature sensor

Lean

Lean/Rich

Air fuel ratio sensor malfunction

  • Air fuel ratio sensor

B

Rich

Lean/Rich

Air fuel ratio sensor malfunction

  • Air fuel ratio sensor
  • Lean: During Control the Injection Volume, the air fuel ratio sensor output voltage (AFS Voltage B1S1) is consistently higher than 3.4 V, and the heated oxygen sensor output voltage (O2S B1S2) is consistently below 0.4 V.
  • Rich: During Control the Injection Volume, the AFS Voltage B1S1 is consistently below 3.1 V, and the O2S B1S2 is consistently higher than 0.55 V.
  • Lean/Rich: During Control the Injection Volume of the Active Test, the output voltage of the heated oxygen sensor alternates correctly.

HINT:

Refer to "Data List / Active Test" [AFS Voltage B1S1, O2S B1S2] (See page ).



B

GO TO STEP 11


A

5.

READ VALUE USING TECHSTREAM (COOLANT TEMP)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine / Data List / Coolant Temp.

(e) Read the Data List twice, when the engine is both cold and warmed up.

Standard value:

With cold engine: Same as ambient air temperature.

With warm engine:

Between 75 and 100°C (167°F and 212°F).

HINT:

Perform "Inspection After Repair" after replacing the engine coolant temperature sensor (See page ).



NG

REPLACE ENGINE COOLANT TEMPERATURE SENSOR


OK

6.

READ VALUE USING TECHSTREAM (MAF)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine / Data List / MAF and Coolant Temp.

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

(f) Read MAF with the engine speed at 3000 rpm.

Standard:

Between 8.5 and 12.5 gm/s (shift lever: N position, A/C: Off).


NG

GO TO STEP 16


OK

7.

CHECK FUEL PRESSURE

(a) Check the fuel pressure (See page ).



NG

REPAIR OR REPLACE FUEL SYSTEM


OK

8.

CHECK FOR EXHAUST GAS LEAK

(a) Check for exhaust gas leaks.

OK:

No gas leaks.

HINT:

Perform "Inspection After Repair" after repairing or replacing the exhaust system (See page ).



NG

REPAIR OR REPLACE EXHAUST SYSTEM


OK

9.

CHECK FOR SPARK (SPARK TEST)

(a) Perform a spark test (See page ).


HINT:

  • If the result of the spark test is normal, proceed to the next step.
  • If the spark plugs or ignition system malfunctions, engine misfire may occur. The misfire count can be read using the Techstream. Enter the following menus: Powertrain / Engine / Data List / Gas Misfire / Cylinder #1 Misfire Count (to Cylinder #4 Misfire Count).
  • Perform "Inspection After Repair" after repairing or replacing the ignition system (See page ).


NEXT

10.

INSPECT FUEL INJECTOR ASSEMBLY (INJECTION AND VOLUME)

(a) Check the injection and volume.

HINT:

  • Refer to the fuel injector assembly inspection procedure (See page ).

  • If the fuel injector assemblies malfunction, engine misfire may occur. The misfire count can be read using the Techstream. Enter the following menus: Powertrain / Engine / Data List / Gas Misfire / Cylinder #1 Misfire Count (to Cylinder #4 Misfire Count).
  • Perform "Inspection After Repair" after replacing the fuel injector assembly (See page ).


OK

GO TO STEP 15


NG

REPLACE FUEL INJECTOR ASSEMBLY

11.

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)



NG

REPLACE AIR FUEL RATIO SENSOR


OK

12.

CHECK TERMINAL VOLTAGE (POWER SOURCE OF AIR FUEL RATIO SENSOR)



NG

GO TO STEP 21


OK

13.

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



NG

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


OK

14.

REPLACE AIR FUEL RATIO SENSOR

(a) Replace the air fuel ratio sensor (See page ).


HINT:

Perform "Inspection After Repair" after replacing the air fuel ratio sensor (See page ).



NEXT

15.

PERFORM CONFIRMATION DRIVING PATTERN

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON and turn the Techstream on.

(c) Clear the DTCs (See page ).


(d) Turn the ignition switch off and wait for at least 30 seconds.

(e) Turn the ignition switch to ON and turn the Techstream on.

(f) Start the engine and warm it up.

(g) Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.

(h) Enter the following menus: Powertrain / Engine / Trouble Codes.

(i) Read the DTCs.

Result

Proceed to

DTC P0171 or P0172 is output

A

DTC is not output

B


B

END


A

16.

CHECK HARNESS AND CONNECTOR

(a) Check the connection and terminal contact pressure of connectors and wire harness between the mass air flow meter and ECM (See page ).


HINT:

Repair any problems.


NEXT

17.

CHECK WHETHER DTC OUTPUT RECURS (DTC P0171 OR P0172)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON and turn the Techstream on.

(c) Clear the DTCs (See page ).


(d) Turn the ignition switch off and wait for at least 30 seconds.

(e) Turn the ignition switch to ON and turn the Techstream on.

(f) Start the engine and warm it up.

(g) Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.

(h) Enter the following menus: Powertrain / Engine / Trouble Codes.

(i) Read the DTCs.

Result

Proceed to

DTC P0171 or P0172 is output

A

DTC is not output

B


B

END


A

18.

CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER - ECM)



NG

REPAIR OR REPLACE HARNESS OR CONNECTOR


OK

19.

REPLACE MASS AIR FLOW METER

(a) Replace the mass air flow meter (See page ).


HINT:

  • If the result of the inspection performed in step 6 indicated no problem, proceed to the next step without replacing the mass air flow meter.
  • Perform "Inspection After Repair" after replacing the mass air flow meter (See page ).


NEXT

20.

CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON and turn the Techstream on.

(c) Clear the DTCs (See page ).


(d) Turn the ignition switch off and wait for at least 30 seconds.

(e) Turn the ignition switch to ON and turn the Techstream on.

(f) Start the engine and warm it up.

(g) Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.

(h) Enter the following menus: Powertrain / Engine / Trouble Codes.

(i) Read the DTCs.

Result

Proceed to

DTC is not output

A

DTC P0171 or P0172 is output

B


A

END


B

REPLACE ECM

21.

CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - EFI MAIN NO. 2 RELAY)



NG

REPAIR OR REPLACE HARNESS OR CONNECTOR


OK

22.

INSPECT ENGINE ROOM JUNCTION BLOCK ASSEMBLY (EFI MAIN NO. 2 RELAY)

(a) Inspect the engine room junction block assembly (See page ).



OK

REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - EFI MAIN MO. 2 RELAY)


NG

REPLACE ENGINE ROOM JUNCTION BLOCK ASSEMBLY

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