Dtc P0171 System Too Lean (Bank 1)

DESCRIPTION

MONITOR DESCRIPTION

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

CONFIRMATION DRIVING PATTERN

WIRING DIAGRAM

INSPECTION PROCEDURE

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

CHECK PCV HOSE CONNECTIONS

CHECK INTAKE SYSTEM

PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE INJECTION VOLUME)

READ VALUE USING TECHSTREAM (COOLANT TEMP)

READ VALUE USING TECHSTREAM (MAF)

CHECK FUEL PRESSURE

CHECK FOR EXHAUST GAS LEAK

CHECK FOR SPARK (SPARK TEST)

INSPECT FUEL INJECTOR ASSEMBLY (INJECTION AND VOLUME)

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

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

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

REPLACE AIR FUEL RATIO SENSOR

CHECK WHETHER DTC OUTPUT RECURS (DTC P0171 OR P0172)

CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER CONNECTOR CONNECTION)

CHECK WHETHER DTC OUTPUT RECURS (DTC P0171 OR P0172)

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

REPLACE MASS AIR FLOW METER

CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED

INSPECT FUSE (EFI NO. 2 FUSE)

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 duration. The fuel trim consists of both the short-term and 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 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	With warm engine and stable air fuel ratio feedback, fuel trim considerably in error to lean side (2 trip detection logic)	Intake system Injector blockage Mass air flow meter Engine coolant temperature sensor Fuel pressure Gas leaks from exhaust system Open or short in air fuel ratio sensor (sensor 1) circuit Air fuel ratio sensor (sensor 1) PCV valve and hose PCV hose connections ECM Wire harness or connector
P0172	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 Mass air flow meter Engine coolant temperature sensor Ignition system Fuel pressure Gas leaks from exhaust system Open or short in air fuel ratio sensor (sensor 1) circuit Air fuel ratio sensor (sensor 1) ECM Wire harness or connector

HINT:

1. When DTC P0171 is set, the actual air fuel ratio is on the lean side. When DTC P0172 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 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.
   

MONITOR DESCRIPTION

Under closed-loop fuel control, a fuel injection volume that deviates from that 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 value. Deviations from the ECM's estimated fuel injection volume also affects 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 a malfunction threshold, the ECM interprets this a fault in the fuel system and sets a DTC.
Example:
The average fuel trim learning value is more than +35% or less than -35%, 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

Monitor runs whenever following DTCs not present	P0010 (VVT Oil Control Valve) P0011 (VVT System - Advance) P0012 (VVT System - Retard) P0013 (Exhaust VVT Oil Control Valve) P0014 (Exhaust VVT System - Advance) P0015 (Exhaust VVT System - Retard) P0016 (VVT System - Misalignment) P0017 (Exhaust VVT System - Misalignment) P0031, P0032 (Air Fuel Ratio Sensor Heater - Sensor 1) 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 Engine Coolant Temperature for Closed Loop Fuel Control) P0335 (Crankshaft Position Sensor) P0340, P0342, P0343 (Camshaft Position Sensor) P0351, P0352, P0353, P0354 (Igniter) P0365, P0367, P0368 (Exhaust Camshaft Position Sensor) P0500 (Vehicle Speed Sensor) P219A (Air Fuel Ratio Imbalance)
Fuel system status	Closed-loop
Battery voltage	11 V or more
Either of following conditions 1 or 2 set	-
1. Engine speed	Less than 720 rpm
2. Engine load	13% or more
Catalyst monitor	No executed

TYPICAL MALFUNCTION THRESHOLDS

EVAP 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 operation) (COROLLA_ZRE142 RM000000PDK0ZAX.html).
   
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 a speed between 37 and 84 mph (60 and 135 km/h) 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.

11. If no pending DTC is output, perform a universal trip and check for permanent DTCs (COROLLA_ZRE142 RM000000PDK0ZAX.html).
    

    HINT:

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

WIRING DIAGRAM

Refer to DTC P0102 (COROLLA_ZRE142 RM000000U5B0NJX_07.html).

INSPECTION PROCEDURE

HINT:

1. Read freeze frame data using the Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.
   
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.
   
4. Sensor 1 refers to the sensor closest to the engine assembly.
   
5. Sensor 2 refers to the sensor farthest away from the engine assembly.
   

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

1. Connect the Techstream to the DLC3.
   

2. Turn the ignition switch to ON.
   

3. Turn the Techstream on.
   

4. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
   

5. 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 (COROLLA_ZRE142 RM000000PDF0G8X.html)

A

2.CHECK PCV HOSE CONNECTIONS

1. Inspect the PCV hose connections (COROLLA_ZRE142 RM000002WZK01NX.html).
   

   OK:

   PCV hose is connected correctly and is not damaged.
   

NG	REPAIR OR REPLACE PCV HOSE

OK

3.CHECK INTAKE SYSTEM

1. Check the intake system for vacuum leaks (COROLLA_ZRE142 RM000003410016X.html).
   

   OK:

   No leaks in intake system.
   

NG	REPAIR OR REPLACE INTAKE SYSTEM

OK

4.PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE INJECTION VOLUME)

1. Connect the Techstream to the DLC3.
   

2. Start the engine.
   

3. Turn the Techstream on.
   

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

5. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume / All Data / AFS Voltage B1S1 and O2S B1S2.
   

6. Perform the Control the Injection Volume operation with the engine idling.
   

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

   HINT:

   1. Change the fuel injection volume within the range of -12% to +12%. The injection volume can be changed in fine gradations.
      
   2. 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.
      
   3. If there is almost no response from the air fuel ratio sensor, a malfunction of the air fuel ratio sensor is suspected.
      
   
   

   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

   
   

   Result

   Status of AFS Voltage B1S1	Status of O2S B1S2	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 assembly blockage Gas leaks from exhaust system Intake system Fuel pressure Mass air flow meter assembly Engine coolant temperature sensor	A
   Rich	Rich	Actual air fuel ratio rich	Fuel injector assembly leakage or blockage Gas leaks from exhaust system Ignition system Fuel pressure Mass air flow meter assembly Engine coolant temperature sensor	A
   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	B

   Lean: During the Control the Injection Volume 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 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 Active Test, the output voltage of the heated oxygen sensor alternates correctly.
   

   HINT:

   Refer to "Data List / Active Test" [AFS Voltage B1S1 and O2S B1S2] (COROLLA_ZRE142 RM000000PDN0MHX.html).

B	Go to step 11

A

5.READ VALUE USING TECHSTREAM (COOLANT TEMP)

1. Connect the Techstream to the DLC3.
   

2. Turn the ignition switch to ON.
   

3. Turn the Techstream on.
   

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

5. Read the Coolant Temp 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 and 212°F).
   

NG	REPLACE ENGINE COOLANT TEMPERATURE SENSOR (COROLLA_ZRE142 RM0000030LG014X.html)

OK

6.READ VALUE USING TECHSTREAM (MAF)

1. Connect the Techstream to the DLC3.
   

2. Turn the ignition switch to ON.
   

3. Turn the Techstream on.
   

4. Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / MAF, Coolant Temp and Engine Speed.
   

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

6. Read MAF with the engine speed at 3000 rpm.
   

   Standard:

   Between 5 and 10 gm/s (Shift lever: Neutral; A/C: Off).
   

NG	Go to step 16

OK

7.CHECK FUEL PRESSURE

1. Check the fuel pressure (COROLLA_ZRE142 RM000001IQZ09UX_01_0002.html).
   

NG	REPAIR OR REPLACE FUEL SYSTEM

OK

8.CHECK FOR EXHAUST GAS LEAK

1. Check for exhaust gas leaks.
   

   OK:

   No gas leaks.
   

NG	REPAIR OR REPLACE EXHAUST SYSTEM

OK

9.CHECK FOR SPARK (SPARK TEST)

1. Perform a spark test (COROLLA_ZRE142 RM000001QVP061X_01_0001.html).
   

   HINT:

   1. If the result of the spark test is normal, proceed to the next step.
      
   2. 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 and ECT / Data List / Gas Misfire / Cylinder #1 Misfire Count (to Cylinder #4 Misfire Count).
      

NEXT

10.INSPECT FUEL INJECTOR ASSEMBLY (INJECTION AND VOLUME)

1. Check the inspection and volume.
   

   HINT:

   1. Refer to the fuel injector assembly inspection procedure (COROLLA_ZRE142 RM000001EDQ04ZX.html).
      
   2. 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 and ECT / Data List / Gas Misfire / Cylinder #1 Misfire Count (to Cylinder #4 Misfire Count).
      

OK	Go to step 15
NG	REPLACE FUEL INJECTOR ASSEMBLY (COROLLA_ZRE142 RM000001EDS05LX.html)

11.INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

1. Inspect the air fuel ratio sensor (COROLLA_ZRE142 RM000001CK8049X.html).
   

NG	REPLACE AIR FUEL RATIO SENSOR (COROLLA_ZRE142 RM00000306S01AX.html)

OK

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

1. Disconnect the air fuel ratio sensor connector.
   

2. Turn the ignition switch to ON.
   

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

   Standard Voltage:

   Tester Connection	Switch Condition	Specified Condition
   B89-2 (+B) - Body ground	Ignition switch ON	11 to 14 V

4. Reconnect the air fuel ratio sensor connector.
   

NG	Go to step 21

OK

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

1. Disconnect the air fuel ratio sensor connector.
   

2. Disconnect the ECM connector.
   

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

   Standard Resistance (Check for Open):

   
   

   Tester Connection	Condition	Specified Condition
   B89-1 (HA1A) - B31-104 (HA1A)	Always	Below 1 Ω

   
   

   Standard Resistance (Check for Short):

   
   

   Tester Connection	Condition	Specified Condition
   B89-1 (HA1A) or B31-104 (HA1A) - Body ground	Always	10 kΩ or higher

4. Reconnect the air fuel ratio sensor connector.
   

5. Reconnect the ECM connector.
   

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

OK

14.REPLACE AIR FUEL RATIO SENSOR

1. Replace the air fuel ratio sensor (COROLLA_ZRE142 RM00000306S01AX.html).
   

NEXT

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

1. Connect the Techstream to the DLC3.
   

2. Turn the ignition switch to ON and turn the Techstream on.
   

3. Clear the DTCs (COROLLA_ZRE142 RM000000PDK0ZAX.html).
   

4. Turn the ignition switch off.
   

5. Turn the ignition switch to ON and turn the Techstream on.
   

6. Start the engine and warm it up.
   

7. Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
   

8. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
   

9. Read the DTCs.
   
   

   Result:

   
   

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

B	END

A

16.CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER CONNECTOR CONNECTION)

1. Check the connection and terminal contact pressure of connectors and wire harness between the mass air flow meter and ECM (COROLLA_ZRE142 RM000000UZ30C8X.html).
   

   HINT:

   Repair any problems.

NEXT

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

1. Connect the Techstream to the DLC3.
   

2. Turn the ignition switch to ON.
   

3. Turn the Techstream on.
   

4. Clear the DTCs (COROLLA_ZRE142 RM000000PDK0ZAX.html).
   

5. Turn the ignition switch off.
   

6. Turn the ignition switch to ON and turn the Techstream on.
   

7. Start the engine and warm it up.
   

8. Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
   

9. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
   

10. Read the DTCs.
    
    

    Result:

    
    

    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)

1. Disconnect the mass air flow meter connector.
   

2. Disconnect the ECM connector.
   

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

   Standard Resistance (Check for Open):

   
   

   Tester Connection	Condition	Specified Condition
   B2-5 (VG) - B31-69 (VG)	Always	Below 1 Ω
   B2-4 (E2G) - B31-92 (E2G)	Always	Below 1 Ω

   
   

   Standard Resistance (Check for Short):

   
   

   Tester Connection	Condition	Specified Condition
   B2-5 (VG) or B31-69 (VG) - Body ground	Always	10 kΩ or higher

4. Reconnect the mass air flow meter connector.
   

5. Reconnect the ECM connector.
   

NG	REPAIR OR REPLACE HARNESS OR CONNECTOR (MASS AIR FLOW METER - ECM)

OK

19.REPLACE MASS AIR FLOW METER

1. Replace the mass air flow meter (COROLLA_ZRE142 RM0000030K7015X.html).
   

   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.

NEXT

20.CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED

1. Connect the Techstream to the DLC3.
   

2. Turn the ignition switch to ON.
   

3. Turn the Techstream on.
   

4. Clear the DTCs (COROLLA_ZRE142 RM000000PDK0ZAX.html).
   

5. Turn the ignition switch off.
   

6. Turn the ignition switch to ON and turn the Techstream on.
   

7. Start the engine and warm it up.
   

8. Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
   

9. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
   

10. Read the DTCs.
    
    

    Result:

    
    

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

B	REPLACE ECM (COROLLA_ZRE142 RM000001CN0030X.html)

A
END

21.INSPECT FUSE (EFI NO. 2 FUSE)

1. Remove the EFI No. 2 fuse from the engine room relay block.
   

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

   Standard Resistance:

   Tester Connection	Condition	Specified Condition
   EFI No. 2 fuse	Always	Below 1 Ω

3. Reinstall the EFI No. 2 fuse.
   

NG	REPLACE FUSE (EFI NO. 2 FUSE)

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