Dtc P0171 System Too Lean (Bank 1)

DESCRIPTION

MONITOR DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

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

CHECK PCV HOSE CONNECTIONS

CHECK AIR INDUCTION SYSTEM

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

READ VALUE USING INTELLIGENT TESTER (COOLANT TEMP)

READ VALUE USING INTELLIGENT TESTER (MAF)

CHECK FUEL PRESSURE

CHECK FOR EXHAUST GAS LEAKS

CHECK FOR SPARKS AND IGNITION

INSPECT FUEL INJECTOR ASSEMBLY (INJECTION AND VOLUME)

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

INSPECT INTEGRATION RELAY (A/F RELAY)

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

REPLACE AIR FUEL RATIO SENSOR

PERFORM CONFIRMATION DRIVING PATTERN

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

INSPECT FUSE (A/F FUSE)

DESCRIPTION

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.
   

MONITOR DESCRIPTION

1. When the average fuel trim learning value is more than +35% or less than -35%, the ECM interprets this as a fuel system malfunction.
   
   
   
   
   
   

WIRING DIAGRAM

INSPECTION PROCEDURE

HINT:

For use of the intelligent tester only:

Malfunctioning areas can be identified by performing the Control the Injection Volume for A/F Sensor function provided in the Active Test. The Control the Injection Volume for A/F Sensor 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 Control the Injection Volume for A/F Sensor operation using the intelligent tester.

1. Connect the intelligent tester to the DLC3.
   
2. Start the engine and turn the tester on.
   
3. Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
   
4. Select the following menu items on the tester: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.
   
5. Perform the Control the Injection Volume for A/F Sensor operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).
   
6. Monitor the voltage outputs 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 Control the Injection Volume for A/F Sensor 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 voltage:

   
   

   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 delay of approximately 20 seconds.

   
   

   Case	Air Fuel Ratio Sensor (Sensor 1) Output Voltage	Heated Oxygen Sensor (Sensor 2) Output Voltage	Main Suspected Trouble Area
   1			-
   2			Air fuel ratio sensor Air fuel ratio sensor heater Air fuel ratio sensor circuit
   3			Heated oxygen sensor Heated oxygen sensor heater Heated oxygen sensor circuit
   4			Fuel pressure Gas leakage from exhaust system (Air fuel ratio extremely lean or rich)

1. Following the Control the Injection Volume for A/F Sensor procedure enables technicians to check and graph the voltage outputs of both the A/F and HO2 sensors.
   
2. The following A/F Control procedure enables the technician to check and graph the voltage output of both the heated oxygen sensors. To display the graph, select the following menu items on the tester: View / Line graph.
   

   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 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 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 lean air-fuel mixture. Check for conditions that would cause the engine to run lean.
      

1. Connect the intelligent tester to the DLC3.
   

2. Turn the ignition switch to the ON position and turn the tester on.
   

3. Select the following menu items: Powertrain / Engine and ECT / DTC.
   

4. Read the 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.

OK:

PCV hose is connected correctly and is not damaged.

1. Check the air induction system for vacuum leakage.
   

   OK:

   No leakage from the air induction system.
   

1. Connect the intelligent tester to the DLC3.
   

2. Start the engine and turn the tester on.
   

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

4. Select the following menu items on the tester: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.
   

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

6. Monitor the voltage outputs 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 Control the Injection Volume for A/F Sensor 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 voltage:

   
   

   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	Suspected Trouble Area	Proceed to
   Lean/Rich	Lean/Rich	Normal	-	C
   Lean/Lean	Lean/Lean	Actual air-fuel ratio lean	PCV valve and hose PCV hose connections Injector blockage Gas leakage from exhaust system Air induction system Fuel pressure Mass Air Flow (MAF) meter Engine Coolant Temperature (ECT) sensor	A
   Rich/Rich	Rich/Rich	Actual air-fuel ratio rich	Injector leakage or blockage Gas leakage from exhaust system Ignition system Fuel pressure MAF meter ECT sensor	A
   Lean/Lean	Lean/Rich	A/F sensor malfunction	A/F sensor	B
   Rich/Rich	Lean/Rich	A/F sensor malfunction	A/F sensor	B

   Lean: During Control the Injection Volume for A/F Sensor, 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 Control the Injection Volume for A/F Sensor, the AFS is consistently less than 3.0 V, and the O2S is consistently more than 0.55 V.
   Lean/Rich: During Control the Injection Volume for A/F Sensor of the Active Test, the output voltage of the heated oxygen sensor alternates correctly.
   

1. Connect the intelligent tester to the DLC3.
   

2. Turn the ignition switch to the ON position and turn the tester on.
   

3. Select the following menu items: Powertrain / Engine and ECT / Data List / Coolant Temp.
   

4. 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°C and 95°C (167°F and 203°F)
   

1. Connect the intelligent tester to the DLC3.
   

2. Turn the ignition switch to the ON position and turn the tester on.
   

3. Select the following menu items: Powertrain / Engine and ECT / Data List / MAF and Coolant Temp.
   

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

5. Read the MAF with the engine in an idling condition and at an engine speed of 2500 rpm.
   

   Standard:

   MAF when engine is stopped:

   Below 0.7 g/s
   

   MAF while engine is idling:

   Between 2.0 g/s and 5.0 g/s (shift position: N, A/C: OFF).
   

   MAF at an engine speed of 2500 rpm:

   Between 8.0 g/s and 19.0 g/s (shift position: N, A/C: OFF).
   

1. Check the fuel pressure (RAV4_ACA30 RM000001IQZ02HX.html).
   

OK:

No gas leakage.

1. Check for sparks and ignition (RAV4_ACA30 RM000000XH30PTX_10_0005.html).
   

   HINT:

   If the spark plugs or ignition system malfunctions, engine misfire may occur. The misfire count can be read using the intelligent tester. Select the following menu items: Powertrain / Engine and ECT / Data List / Cylinder #1 (to #6) Misfire rate.

1. Inspect the fuel injector assembly (RAV4_ACA30 RM000001IR1014X.html).
   

   HINT:

   If the injectors malfunction, engine misfire may occur. The misfire count can be read using the intelligent tester. Select the following menu items: Powertrain / Engine and ECT / Data List / Cylinder #1 (to #6) Misfire rate.

1. Disconnect the A/F sensor connector.
   

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

   Standard resistance:

   Bank 1:

   Tester Connection	Condition	Specified Condition
   HA1A (1) - +B (2)	20°C (68°F)	1.8 to 3.4 Ω
   HA1A (1) - A1A- (4)	Always	10 kΩ or higher

   Bank 2:

   Tester Connection	Condition	Specified Condition
   HA2A (1) - +B (2)	20°C (68°F)	1.8 to 3.4 Ω
   HA2A (1) - A2A- (4)	Always	10 kΩ or higher

3. Reconnect the A/F sensor connector.
   

1. Remove the integration relay from the engine room No. 1 relay block.
   

2. Measure the A/F relay resistance.
   

   Standard resistance:

   Tester Connection	Specified Condition
   1C-1 - 1B-8	10 kΩ or higher
   1C-1 - 1B-8	Below 1 Ω (when battery voltage is applied to terminals 1B-6 and 1B-7)

3. Reinstall the integration relay.
   

1. Disconnect the A/F sensor connector.
   

2. Measure the resistance.
   
   

   Standard resistance (Check for open):

   Bank 1:

   
   

   Tester Connection	Specified Condition
   HA1A (B7-1) - HA1A (B96-86)	Below 1 Ω
   A1A+ (B7-3) - A1A+ (B96-93)	Below 1 Ω
   A1A- (B7-4) - A1A- (B96-116)	Below 1 Ω

   Bank 2:

   
   

   Tester Connection	Specified Condition
   HA2A (B67-1) - HA2A (B96-109)	Below 1 Ω
   A2A+ (B67-3) - A2A+ (B96-120)	Below 1 Ω
   A2A- (B67-4) - A2A- (B96-119)	Below 1 Ω

   
   

   Standard resistance (Check for short):

   Bank 1:

   
   

   Tester Connection	Specified Condition
   HA1A (B7-1) or HA1A (B96-86) - Body ground	10 kΩ or higher
   A1A+ (B7-3) or A1A+ (B96-93) - Body ground	10 kΩ or higher
   A1A- (B7-4) or A1A- (B96-116) - Body ground	10 kΩ or higher

   Bank 1:

   
   

   Tester Connection	Specified Condition
   HA2A (B67-1) or HA2A (B96-109) - Body ground	10 kΩ or higher
   A2A+ (B67-3) or A2A+ (B96-120) - Body ground	10 kΩ or higher
   A2A- (B67-4) or A2A- (B96-119) - Body ground	10 kΩ or higher

3. Reconnect the ECM connector.
   

4. Reconnect the A/F sensor connector.
   

1. Replace the air fuel ratio sensor (RAV4_ACA30 RM000001RO200SX.html).
   

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

2. Turn the ignition switch to the ON position and turn the tester on (Procedure B).
   

3. Clear the DTCs (RAV4_ACA30 RM000000PDK0WDX.html) (Procedure C).
   

4. Select the check mode using the tester (RAV4_ACA30 RM000000PDL09GX.html) (Procedure D).
   

5. Start the engine and warm it up with all the accessories switched off (Procedure E).
   

6. Drive the vehicle at between 60 km/h and 120 km/h (38 mph and 75 mph) and at an engine speed of between 1400 rpm and 3200 rpm for 3 to 5 minutes (Procedure F).
   

   
   
   
   

   HINT:

   If the system is still malfunctioning, the MIL will be illuminated during procedure "F".

   NOTICE:

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

1. Select the following menu items: Powertrain / Engine and ECT / DTC.
   

2. Read the DTCs.
   
   

   Result:

   
   

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

1. Remove the A/F fuse from the integration relay.
   

2. Measure the fuse resistance.
   

   Standard resistance:

   Below 1 Ω
   

3. Reinstall the fuse.