DTC P0171: System Too Lean (Bank 1); DTC P0172: System Too Rich (Bank 1); DTC P0174: System Too Lean (Bank 2); DTC P0175: System Too Rich (Bank 2): Procedure

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch ON and turn the tester ON.
3. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
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 and P0175 are output, troubleshoot those DTCs first.

B → GO TO DTC CHART 

A: Go to next step 

OK

PCV hose is connected correctly and is not damaged.

NG → REPAIR OR REPLACE PCV HOSE 

OK: Go to next step 

1. Check the air induction system for vacuum leaks.

   OK

   No leakage from air induction system.

NG → REPAIR OR REPLACE AIR INDUCTION SYSTEM 

OK: Go to next step 

1. Connect the Techstream 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. On the tester, enter the following menus: 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 outputs of A/F and HO2 sensors (AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2) displayed on the tester.

   HINT: 

   • 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 %.
   • Each sensor reacts in accordance with increases 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	Misfires	Suspected Trouble Area	Proceed to
   Lean/Rich	Lean/Rich	Normal	-	-	C
   Lean	Lean	Actual air fuel ratio lean	May occur	PCV valve and hose Ventilation 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	Actual air fuel ratio lean	-	Injector leakage or blockage Gas leakage from exhaust system Injection system Fuel pressure MAF meter ECT sensor	A
   Lean	Lean/Rich	A/F sensor malfunction	-	A/F sensor	B
   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.

C → See step   15 

B → See step   11 

A: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch ON and turn the tester ON.
3. Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / Coolant Temp.
4. Read the Coolant Temp value when the engine is cold and warmed up.

   Standard

   ECT when the engine is cold: Same as ambient temperature

   ECT when the engine is warmed up: 75 to 95°C (167 to 203°F)

NG → REPLACE ENGINE COOLANT TEMPERATURE SENSOR 

OK: Go to next step 

1. Inspect the output voltage.
   Fig 1: Identifying Resistance & Temperature Graph

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   1. Apply battery voltage across terminals 3 (+B) and 4 (E2G).
   2. Connect the positive (+) tester probe to terminal 5 (VG), and the negative (-) tester probe to terminal 4 (E2G).
   3. Blow air into the MAF meter.

      Standard condition

      Voltage fluctuates

2. Inspect the resistance.
   1. )Using an ohmmeter, measure the resistance between terminals 2 (THA) and 1 (E2).

      Standard resistance

      12.5 to 16.9 kΩ at -20°C (-4°F)

      2.19 to 2.67 kΩ at 20°C (68°F)

      0.50 to 0.68 kΩ at 60°C (140°F)

3. If using a intelligent tester:
   Fig 2: Identifying Mass Air Flow Meter

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Inspect the mass air flow meter.

   1. Connect the intelligent tester to the DLC3.
   2. Turn the ignition switch to the ON position.
   3. Blow air into the MAF meter.

      Standard condition

      Air flow value of the CURRENT DATA changes

4. If not using a intelligent tester:
   Fig 3: Connecting Positive Tester Probe Of Voltmeter

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Inspect the mass air flow meter.

   1. Turn the ignition switch to the ON position.
   2. Connect the positive tester probe of the voltmeter to terminal VG of the ECM and the negative tester probe of the voltmeter to terminal E2G of the ECM.
   3. Blow air into the air flow meter.

      Standard condition

      Voltage fluctuates

NG → REPLACE MASS AIR FLOW METER 

OK: Go to next step 

1. Check the fuel pressure. Refer to ON-VEHICLE INSPECTION - Step 2 .

NG → REPAIR OR REPLACE FUEL SYSTEM 

OK: Go to next step 

OK

No gas leakage.

NG → REPAIR OR REPLACE EXHAUST SYSTEM 

OK: Go to next step 

1. Check for spark and ignition See step  7.

   HINT: 

   If the spark plugs or ignition system malfunction, engine misfire may occur. The misfire counter can be read with the Techstream. Enter the following menus: Powertrain / Engine and ECT / Data List / Misfire / Cylinder #1 Misfire Count (to Cylinder #8 Misfire Count).

NG → REPAIR OR REPLACE IGNITION SYSTEM 

OK: Go to next step 

1. Inspect the fuel injector. Refer to INSPECTION .

   HINT: 

   If the injectors are malfunctioning, engine misfire may occur. The misfire counter can be read with the Techstream. Enter the following menus: Powertrain / Engine and ECT / Data List / Misfire / Cylinder #1 Misfire Count (to Cylinder #8 Misfire Count).

NG → REPLACE FUEL INJECTOR 

OK: Go to next step 

1. Disconnect the A41 or A42 Air Fuel Ratio (A/F) sensor connector.
   Fig 4: Inspecting Air Fuel Ratio Sensor (Heater Resistance)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the resistance of the A/F sensor.

   Standard resistance

   Tester Connection	Specified Condition
   HT (1) - +B (2)	1.8 to 3.4 kΩ at 20°C (68°F)
   HT (1) - A- (4)	10 kΩ or higher

NG → REPLACE AIR FUEL RATIO SENSOR 

OK: Go to next step 

1. Remove the A/F relay from the engine room R/B.
   Fig 5: Identifying Relay Test Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the resistance of the A/F relay.

   Standard resistance

   Terminal Connection	Specified Condition
   3 - 5	10 kΩ or higher
   3 - 5	Below 1 Ω (when battery voltage is applied to terminals 1 and 2)

NG → REPLACE A/F RELAY 

OK: Go to next step 

1. Disconnect the A41 or A42 A/F sensor connector.
   Fig 6: Identifying A41 & A42 A/F Sensor Connector Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Turn the ignition switch ON.
3. Measure the voltage between the +B terminal of the A/F sensor connector and body ground.

   Standard voltage

   Tester Connection	Specified Condition
   +B (A41-2) - Body ground	9 to 14 V
   +B (A42-2) - Body ground

4. Turn the ignition switch OFF.
5. Disconnect the E6 ECM connector.
6. Check the resistance.

   Standard resistance (Check for open)

   Tester Connection	Specified Condition
   HT (A41-1) - HA1A (E6-2) HT (A42-1) - HA2A (E6-1)	Below 1 Ω
   A+ (A41-3) - A1A+ (E6-22) A+ (A42-3) - A2A+ (E6-23)
   A- (A41-4) - A1A- (E6-30) A- (A42-4) - A2A- (E6-31)

   Standard resistance (Check for short)

   Tester Connection	Specified Condition
   HT (A41-1) or HA1A (E6-2) - Body ground HT (A42-1) or HA2A (E6-1) - Body ground	10 kΩ or higher
   A+ (A41-3) or A1A+ (E6-22) - Body ground A+ (A42-3) or A2A+ (E6-23) - Body ground
   A- (A41-4) or A1A- (E6-30) - Body ground A- (A42-4) or A2A- (E6-31) - Body ground

7. Reconnect the ECM connector.
8. Reconnect the A/F sensor connector.
   Fig 7: Identifying A/F Sensor & ECM Circuit Diagram

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

NEXT: Go to next step 

Fig 8: Identifying Confirmation Driving Pattern Of Vehicle Speed

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Connect the Techstream to the DLC3 [A].
2. Turn the ignition switch ON and turn the tester ON [B].
3. Clear DTCs. Refer to DTC CHECK / CLEAR [C].
4. Switch the ECM from normal mode to check mode using the tester. Refer to CHECK MODE PROCEDURE [D].
5. Start the engine and warm it up with all the accessories switched OFF [E].
6. Drive the vehicle at between 38 and 75 mph (60 and 120 km/h) and at an engine speed of between 1400 RPM and 3200 RPM for 3 to 5 minutes [F].

   HINT: 

   If the system is still malfunctioning, the MIL will be illuminated during step [F].

   NOTE:

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

NEXT: Go to next step 

1. On the Techstream, enter the following menu: Powertrain / Engine and ECT / Trouble Codes.
2. Read the DTCs.

   Result

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

B → See step   5 

A → END