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 engine switch on (IG).
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine / Trouble Codes.
5. Read the DTCs.

   Result

   Result	Proceed to
   DTC P0171, P0172, P0174 or P0175 is output	A
   DTC 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 → See step   27 

A: Go to next step 

1. Check the PCV hose connections. Refer to ON-VEHICLE INSPECTION - Step 1 .

   OK

   PCV valve and hose are connected correctly and are not damaged.

NG → REPAIR OR REPLACE PCV HOSE 

OK: Go to next step 

1. Check the air induction system for vacuum leaks. Refer to ON-VEHICLE INSPECTION .

   OK

   No leaks in 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.
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 / Active Test / Control the Injection Volume / All Data / AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2.
6. Perform the Control the Injection Volume operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume).
7. Monitor the voltage outputs of the air fuel ratio sensor and the heated oxygen sensor (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% 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 or AFS Voltage B2S1 (Air fuel ratio)	+12%	Rich	Below 3.1 V
   	-12%	Lean	Higher than 3.4 V
   O2S B1S2 or O2S B2S2 (Heated oxygen)	+12%	Rich	Higher than 0.55 V
   	-12%	Lean	Below 0.4 V

   Result

   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	Misfire	Suspected Trouble Area	Proceed to
   Lean/Rich	Lean/Rich	Normal	-	-	A
   Lean	Lean	Actual air fuel ratio lean	May occur	PCV valve and hose PCV hose connections Fuel injector assembly blockage Gas leak from exhaust system Air induction 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 the Control the Injection Volume for A/F Sensor Active Test, the air fuel ratio sensor output voltage (AFS Voltage) is consistently more than 3.4 V, and the heated oxygen sensor output voltage (O2S) is consistently less than 0.4 V.
   • Rich: During the Control the Injection Volume for A/F Sensor Active Test, the AFS Voltage is consistently less than 3.1 V, and the O2S is consistently more 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.

   HINT: 

   Refer to "Data List / Active Test" [AFS Voltage B1S1, AFS Voltage B2S1, O2S B1S2 and O2S B2S2]. Refer to DATA LIST / ACTIVE TEST .

B → See step   13 

A: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the engine switch on (IG).
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine / Data List / All Data / Coolant Temp.
5. 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).

NG → See step   28 

OK: Go to next step 

1. Connect the Techstream to the DLC3.
2. Start the engine.
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine / Data List / All Data / MAF and Coolant Temp.
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 7.60 g/sec. and 11.40 g/sec. (shift lever: Neutral position, A/C: Off).

NG → See step   18 

OK: Go to next step 

1. Check the fuel pressure (low pressure side). Refer to ON-VEHICLE INSPECTION - Step 2 .

NG → REPAIR OR REPLACE FUEL SYSTEM (LOW PRESSURE SIDE) 

OK: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the engine switch on (IG) and turn the Techstream on.
3. Start the engine.
4. Enter the following menus: Powertrain / Engine / Data List / Fuel Press.
5. While revving the engine, check that the fuel pressure fluctuates.

   OK

   Fuel pressure fluctuates.

NG → See step   32 

OK: Go to next step 

1. Check the fuel pressure (high pressure side). Refer to ON-VEHICLE INSPECTION - Step 3 .

NG → REPAIR OR REPLACE FUEL SYSTEM 

OK: Go to next step 

1. Check for exhaust gas leaks.

   OK

   No gas leaks.

NG → REPAIR OR REPLACE EXHAUST SYSTEM 

OK: Go to next step 

1. Perform a spark test. Refer to ON-VEHICLE INSPECTION .

   HINT: 

   If the result of the spark test is normal, proceed to the next step.

NEXT: Go to next step 

1. Check the injection and volume.

   HINT: 

   • Refer to the fuel injector assembly inspection procedure. Refer to INSPECTION .
   • If the injectors 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 #6 Misfire Count).
2. Inspect the cold start injector. Refer to INSPECTION .

OK → See step   17 

NG → See step   29 

NG → See step   30 

OK: Go to next step 

NG → See step   23 

OK: Go to next step 

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

OK: Go to next step 

1. Replace the air fuel ratio sensor. Refer to REMOVAL .

NEXT: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the engine switch on (IG) and turn the Techstream on.
3. Clear the DTCs. Refer to DTC CHECK / CLEAR .
4. Turn the engine switch off and wait for at least 30 seconds.
5. Turn the engine switch on (IG) 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 / Trouble Codes.
9. Read the DTCs.

   Result

   Result	Proceed to
   DTC P0171, P0172, P0174 or P0175 is output	A
   DTC is not output	B

B → END 

A: Go to next step 

1. Check the connection and terminal contact pressure of connectors and wire harness between the mass air flow meter and ECM. Refer to ELECTRONIC CIRCUIT INSPECTION PROCEDURE .

   HINT: 

   Repair any problems.

NEXT: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the engine switch on (IG) and turn the Techstream on.
3. Clear the DTCs. Refer to DTC CHECK / CLEAR .
4. Turn the engine switch off and wait for at least 30 seconds.
5. Turn the engine switch on (IG) 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 / Trouble Codes.
9. Read the DTCs.

   Result

   Result	Proceed to
   DTC P0171, P0172, P0174 or P0175 is output	A
   DTC is not output	B

B → END 

A: Go to next step 

1. Disconnect the E29 MAF meter connector.
2. Disconnect the E5 ECM connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard resistance (Check for open)

   Tester Connection	Specified Condition
   E29-5 (VG) - E5-27 (VG)	Below 1 Ω
   E29-4 (E2G) - E5-26 (E2G)	Below 1 Ω

   Standard resistance (Check for short)

   Tester Connection	Specified Condition
   E29-5 (VG) or E5-27 (VG) - Body ground	10 kΩ or higher

4. Reconnect the MAF meter connector.
5. Reconnect the ECM connector.

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

OK: Go to next step 

1. Replace the mass air flow meter. Refer to REMOVAL .

   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: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the engine switch on (IG) and turn the Techstream on.
3. Clear the DTCs. Refer to DTC CHECK / CLEAR .
4. Turn the engine switch off and wait for at least 30 seconds.
5. Turn the engine switch on (IG) 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 / Trouble Codes.
9. Read the DTCs.

   Result

   Result	Proceed to
   DTC is not output	A
   DTC P0171, P0172, P0174 or P0175 is output	B

B → See step   31 

A → END 

NG → REPLACE RELAY (A/F RELAY) 

OK: Go to next step 

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR (A/F RELAY - BATTERY) 

OK: Go to next step 

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → REPAIR OR REPLACE HARNESS OR CONNECTOR (EFI MAIN RELAY - A/F RELAY)