Toyota Tundra Service Manual: System Too Lean (Bank 1) (P0171,P0172,P0174,P0175)

Toyota Tundra Service Manual / Engine, Hybrid System / 1ur-fe Engine Control / Sfi System / System Too Lean (Bank 1) (P0171,P0172,P0174,P0175)

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 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 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.

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)

  • Air induction system
  • Injector blockage
  • Mass Air Flow (MAF) meter
  • Engine Coolant Temperature (ECT) sensor
  • Fuel pressure
  • Gas leak from exhaust system
  • Open or short in A/F sensor (for Sensor 1) circuit
  • A/F sensor (for Sensor 1)
  • A/F sensor heater (for Sensor 1)
  • Integration relay
  • A/F sensor heater and integration relay circuits
  • PCV valve and hose
  • PCV hose connections
  • EGR valve assembly
  • ECM
  • Wire harness or connector

P0172

P0175

With warm engine and stable air-fuel ratio feedback, fuel trim considerably in error to rich side

(2 trip detection logic)

  • Injector leak or blockage
  • MAF meter
  • ECT sensor
  • Ignition system
  • Fuel pressure
  • Gas leak from exhaust system
  • Open or short in A/F sensor (for Sensor 1) circuit
  • A/F sensor (for Sensor 1)
  • A/F sensor heater (for Sensor 1)
  • Integration relay
  • A/F sensor heater and integration relay circuits
  • EGR valve assembly
  • ECM
  • Wire harness or connector

HINT:

  • When DTC P0171 or P0174 is stored, the actual air-fuel ratio is on the lean side. When DTC P0172 or P0175 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 or P0174 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 ECM estimated fuel injection volumes also affect the average fuel trim learning value, which is a combination of the average short-term fuel trim (fuel feedback compensation value) and the average long-term fuel trim (learning value of the air-fuel ratio). If the average fuel trim learning 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 learning 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 (for Bank 1)

P0172: Fuel trim rich (for Bank 1)

P0174: Fuel trim lean (for Bank 2)

P0175: Fuel trim rich (for Bank 2)

Required Sensors/Components

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

Monitor runs whenever following DTCs not present

P0010, P0020 (VVT oil control valve)

P0011, P0021 (VVT system - Advance)

P0012, P0022 (VVT system - Retard)

P0013, P0023 (Exhaust VVT oil control valve)

P0014, P0024 (Exhaust VVT system - Advance)

P0015, P0025 (Exhaust VVT system - Retard)

P0016, P0018 (VVT system - Misalignment)

P0017, P0019 (Exhaust VVT system - Misalignment)

P0031, P0032, P0051, P0052, P101D, P103D (Air fuel ratio sensor heater)

P006A, P0107, P0108 (Manifold absolute pressure)

P0102, P0103 (Mass air flow meter)

P0115, P0117, P0118 (Engine coolant temperature sensor)

P0120, P0121, P0122, P0123, P0220, P0222, P0223, P2135 (Throttle position sensor)

P0125 (Insufficient Coolant Temperature for Closed Loop Fuel Control)

P0335 (Crankshaft position sensor)

P0340, P0342, P0343, P0345, P0347, P0348 (VVT sensor)

P1340 (Camshaft position sensor)

P0351 - P0358 (Igniter)

P0365, P0367, P0368, P0390, P0392, P0393 (Exhaust VVT sensor)

P0401 (EGR system)

P0412, P0415, P0418, P0419, P1613, P1614 (Secondary Air Injection System Control)

P0500 (Vehicle speed sensor)

P219A, P219B, P219C, P219D, P219E, P219F, P21A0, P21A1, P21A2, P21A3 (Air-fuel ratio imbalance)

P2440, P2441, P2442, P2443, P2444, P2445, P2446, P2447 (Secondary Air Injection System)

Fuel system status

Closed loop

Battery voltage

11 V or more

Either of following conditions 1 or 2 met

-

1. Engine RPM

Less than 1100 rpm

2. Engine load

11.5% or more

Catalyst monitor

Not executed

TYPICAL MALFUNCTION THRESHOLDS

Purge-cut

Executing

Either of following conditions 1 or 2 met

-

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

35% or more (varies with engine coolant temperature)

2. Average of 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 DTCs (even if no DTCs are stored, perform the clear DTC operation).
  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 120 km/h (37 and 75 mph) and at an engine speed of between 1400 and 3200 rpm for 5 minutes or more [D].

    CAUTION:

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

  9. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes [E].
  10. Read the pending DTCs.

    HINT:

    • If a pending DTC is output, the system is malfunctioning.
    • If a pending DTC is not output, perform the following procedure.
  11. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
  12. Input the DTC: P0171, P0172, P0174 or P0175.
  13. Check the DTC judgment result.

    Tester Display

    Description

    NORMAL

    • DTC judgment completed
    • System normal

    ABNORMAL

    • DTC judgment completed
    • System abnormal

    INCOMPLETE

    • DTC judgment not completed
    • Perform driving pattern after confirming DTC enabling conditions

    N/A

    • Unable to perform DTC judgment
    • Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit

    HINT:

    If the judgment result shows INCOMPLETE or N/A, perform steps [C] through [E] again.

  14. 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 P2195 (See page ).

CAUTION / NOTICE / HINT

HINT:

  • 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.
  • 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.
  • 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.
  • Bank 1 refers to the bank that includes the No. 1 cylinder*.

    *: The No. 1 cylinder is the cylinder which is farthest from the transmission.

  • Bank 2 refers to the bank that does not include the No. 1 cylinder.
  • Sensor 1 refers to the sensor closest to the engine assembly.
  • Sensor 2 refers to the sensor farthest away from the engine assembly.

PROCEDURE

1.

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

(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 and ECT / Trouble Codes.

(e) Read DTCs.

Result

Result

Proceed to

P0171, P0172, P0174 or P0175 is output

A

P0171, P0172, P0174 or P0175 and other DTCs are output

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 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

HINT:

If a malfunction occurs when depressing the brake pedal, inspect the brake booster assembly, as there may be a vacuum leak in the brake booster assembly itself.

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

OK:

No leaks in intake system.

HINT:

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 FOR A/F SENSOR)

(a) Connect the Techstream to the DLC3.

(b) Start the engine.

(c) Turn the Techstream on.

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

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

(f) Perform the Control the Injection Volume for A/F Sensor operation with the engine idling.

(g) Monitor the output voltages of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2) displayed on the Techstream.

HINT:

  • Change the fuel injection volume within the range of -12.5% to +12.5%.
  • 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.

Techstream Display (Sensor)

Injection Volume

Status

Voltage

AFS Voltage B1S1 or AFS Voltage B2S1

(Air fuel ratio)

+12.5%

Rich

Below 3.1 V

AFS Voltage B1S1 or AFS Voltage B2S1

(Air fuel ratio)

-12.5%

Lean

Higher than 3.4 V

O2S B1S2 or O2S B2S2

(Heated oxygen)

+12.5%

Rich

Higher than 0.55 V

O2S B1S2 or O2S B2S2

(Heated oxygen)

-12.5%

Lean

Below 0.4 V

Status of AFS Voltage B1S1 or AFS Voltage B2S1

Status of O2S B1S2 or O2S B2S2

Air Fuel Ratio Condition and Air Fuel Ratio Sensor Condition

Suspected Trouble Area

Proceed to

Lean/Rich

Lean/Rich

Normal

-

A

Lean

Lean

Actual air fuel ratio lean

  • PCV valve and hose
  • PCV hose connections
  • Fuel injector blockage
  • Gas leaks from exhaust system
  • Intake system
  • Fuel pressure
  • Mass air flow meter assembly
  • Manifold absolute pressure sensor
  • Engine coolant temperature sensor
  • EGR valve assembly

A

Rich

Rich

Actual air fuel ratio rich

  • Fuel injector leakage or blockage
  • Gas leaks from exhaust system
  • Ignition system
  • Fuel pressure
  • Mass air flow meter assembly
  • Manifold absolute pressure sensor
  • Engine coolant temperature sensor

A

Lean

Lean/Rich

Air fuel ratio sensor malfunction

  • Air fuel ratio sensor
  • EGR valve assembly

B

Rich

Lean/Rich

Air fuel ratio sensor malfunction

Air fuel ratio sensor

B

Lean: During the Control the Injection Volume for A/F Sensor Active Test, the air fuel ratio sensor output voltage (AFS Voltage) is consistently higher than 3.4 V, and the heated oxygen sensor output voltage (O2S) is consistently below 0.4 V.

Rich: During the Control the Injection Volume for A/F Sensor Active Test, the AFS Voltage is consistently below 3.1 V, and the O2S is consistently higher than 0.55 V.

Lean/Rich: During the Control the Injection Volume for A/F Sensor Active Test, the output voltage of the heated oxygen sensor alternates correctly.

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 and ECT / Data List / Coolant Temp.

(e) Read 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°C 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 and ECT / 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 18.3 gm/sec. and 25.8 gm/sec. (shift lever: N; A/C: Off).

NG

GO TO STEP 18

OK

7.

CHECK FUEL PRESSURE

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

HINT:

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

NG

REPAIR OR REPLACE FUEL SYSTEM

OK

8.

CHECK FOR EXHAUST GAS LEAK

(a) Check for exhaust gas leak.

OK:

No gas leak.

HINT:

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

NG

REPAIR OR REPLACE EXHAUST SYSTEM

OK

9.

CHECK FOR SPARKS AND IGNITION

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

OK:

Sparks jump across electrode gap.

HINT:

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

NG

REPAIR OR REPLACE IGNITION SYSTEM

OK

10.

INSPECT FUEL INJECTOR (INJECTION AND VOLUME)

(a) Check the injection and volume.

HINT:

  • Refer to the fuel injector assembly inspection procedure (See page ).
  • If the injectors malfunction, engine misfire may occur. The misfire count can be read using the Techstream. Enter the following menus: Powertrain / Engine and ECT / Data List / Cylinder #1 Misfire Count (to Cylinder #8 Misfire Count).
  • Perform "Inspection After Repair" after replacing the fuel injector assembly (See page ).
OK

GO TO STEP 15

NG

REPLACE FUEL INJECTOR

11.

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

NG

REPLACE AIR FUEL RATIO SENSOR

OK

12.

CHECK TERMINAL VOLTAGE (+B OF AIR FUEL RATIO SENSOR)

NG

GO TO STEP 23

OK

13.

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

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

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.

(c) Turn the Techstream on.

(d) Clear the DTCs (See page ).

(e) Turn the ignition switch off.

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

(g) Start the engine and warm it up.

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

(i) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

(j) Read DTCs.

Result

Result

Proceed to

DTC P0171, P0172, P0174 or P0175 is output

A

DTC is not output

B

B

END

A

16.

PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE EGR STEP POSITION)

(a) Connect the Techstream to the DLC3.

(b) Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher.

HINT:

  • When performing the Active Test, make sure the shift lever is in P or N.
  • The A/C switch and all accessory switches should be off.

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position.

(e) Confirm that Throttle Idle Position is ON and check the engine idling condition and the value of MAP in the Data List while performing the Active Test.

HINT:

  • Do not leave the EGR valve open for 10 seconds or more during the Active Test.
  • Be sure to return the EGR valve to step 0 when the Active Test is completed.

OK:

MAP and idling condition change in response to EGR step position as follows.

Standard:

-

EGR Step Position (Active Test)

Step 0

Step 0 to 30

Idling condition

Steady idling

Idling changes from steady to rough idling or engine stalls

MAP

(Data List)

20 to 40 kPa (150 to 300 mmHg)

MAP value is at least 10 kPa (75 mmHg) higher than when EGR valve is fully closed

OK

GO TO STEP 18

NG

17.

INSPECT EGR VALVE ASSEMBLY

(a) Remove the EGR valve assembly (See page ).

(b) Check if the EGR valve is stuck open.

OK:

EGR valve is tightly closed.

HINT:

Perform "Inspection After Repair" after replacing the EGR valve assembly (See page ).

NG

REPLACE EGR VALVE ASSEMBLY

OK

18.

CHECK HARNESS AND CONNECTOR

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

HINT:

Repair any problems.

NEXT

19.

CHECK WHETHER DTC OUTPUT RECURS

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Clear the DTCs (See page ).

(e) Turn the ignition switch off.

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

(g) Start the engine and warm it up.

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

(i) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

(j) Read DTCs.

Result

Result

Proceed to

DTC P0171, P0172, P0174 or P0175 is output

A

DTC is not output

B

B

END

A

20.

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

(a) Disconnect the mass air flow meter connector.

(b) Disconnect the ECM connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

D7-3 (VG) - D74-74 (VG)

Always

Below 1 Ω

D7-2 (E2G) - D74-75 (E2G)

Always

Below 1 Ω

D7-3 (VG) or D74-74 (VG) - Body ground

Always

10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

21.

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 assembly.
  • Perform "Inspection After Repair" after replacing the mass air flow meter (See page ).
NEXT

22.

CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Clear the DTCs (See page ).

(e) Turn the ignition switch off.

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

(g) Start the engine and warm it up.

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

(i) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

(j) Read DTCs.

Result

Result

Proceed to

DTC is not output

A

DTC P0171, P0172, P0174 or P0175 is output

B

A

END

B

REPLACE ECM

23.

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

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

24.

INSPECT INTEGRATION RELAY (A/F)

(a) Inspect the integration relay (A/F) (See page ).

OK

CHECK ECM POWER SOURCE CIRCUIT

NG

REPLACE INTEGRATION RELAY

    Open in Secondary Air Injection System Heater Control Circuit (P144C,P144D)

    Bank 1 Air-Fuel Ratio Imbalance (P219A-P219F,P21A0-P21A3)

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