Sfi System - P0175

1. Description

2. Monitor description

3. Monitor strategy

4. Typical enabling conditions

5. Typical malfunction thresholds

6. Wiring diagram

7. Inspection procedure

8. Check any other dtcs output (in addition to dtc p0171, p0172, p0174 or p0175)

9. Check pcv hose connections

10. Check air induction system

11. Perform active test by intelligent tester (a/f control)

12. Read value of intelligent tester (coolant temp)

13. Read value of intelligent tester (maf)

14. Check fuel pressure

15. Check for exhaust gas leakage

16. Check for sparks and ignition

17. Inspect fuel injector assembly (injection and volume)

18. Inspect air fuel ratio sensor (heater resistance)

19. Inspect air fuel ratio sensor heater relay

20. Check harness and connector (a/f sensor - ecm)

21. Replace air fuel ratio sensor

22. Perform confirmation driving pattern

23. Check whether dtc output recurs (dtc p0171, p0172, p0174 or p0175)

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)

​

DESCRIPTION

HINT:

1. When DTC P0171 or P0174 is set, the actual air-fuel ratio is on the lean side. When DTC P0172 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. 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

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

WIRING DIAGRAM

INSPECTION PROCEDURE

HINT:

For use of the intelligent tester only:

Malfunctioning areas can be identified by performing the A/F CONTROL function provided in the ACTIVE TEST. The A/F CONTROL 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 A/F CONTROL 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 2,500 rpm for approximately 90 seconds.
   
4. Select the following menu items on the tester: DIAGNOSIS / ENHANCEDOBD II / ACTIVE TEST / A/F CONTROL.
   
5. Perform the A/F CONTROL 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 A/F CONTROL 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 Volumes	Status	Voltages
   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 output delay of approximately 20 seconds.

   
   

   Case	A/F Sensor (Sensor 1) Output Voltage		HO2 Sensor (Sensor 2) Output Voltage		Main Suspected Trouble Area
   1	Injection Volume +25% -12.5%		Injection Volume +25% -12.5%		-
   	Output Voltage More than 3.35 V Less than 3.0 V		Output Voltage More than 0.55 V Less than 0.4 V
   2	Injection Volume +25% -12.5%		Injection Volume +25% -12.5%		A/F sensor A/F sensor heater A/F sensor circuit
   	Output Voltage Almost no reaction		Output Voltage More than 0.55 V Less than 0.4 V
   3	Injection Volume +25% -12.5%		Injection Volume +25% -12.5%		HO2 sensor HO2 sensor heater HO2 sensor circuit
   	Output Voltage More than 3.35 V Less than 3.0 V		Output Voltage Almost no reaction
   4	Injection volume +25% -12.5%		Injection Volume +25% -12.5%		Injector Fuel pressure Gas leakage from exhaust system (Air-fuel ratio extremely lean or rich)
   	Output Voltage Almost no reaction		Output Voltage Almost no reaction

7. 1. Following the A/F CONTROL procedure enables technicians to check the graph of the voltage outputs of both the A/F and HO2 sensors.
      
   2. To display the graph, select the following menu items on the tester: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL / USER DATA / AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2. Press the YES button and then the ENTER button. Then press the F4 button.
      

      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 on and turn the tester on.

3. Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.

4. Read 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.

B	GO TO DTC CHART

A

OK:

PCV hose is connected correctly and is not damaged.

NG	REPAIR OR REPLACE PCV HOSE

OK

1. Check the air induction system for vacuum leakage.

   OK:

   No leakage from air induction system.
   

NG	REPAIR OR REPLACE AIR INDUCTION SYSTEM

OK

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 2,500 rpm for approximately 90 seconds.

4. Select the following menu items on the tester: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.

5. Perform the A/F CONTROL 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 A/F and HO2 sensors (AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2) displayed on the tester.

   HINT:

   1. The A/F CONTROL 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 Volumes	Status	Voltages
   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 Areas	Proceed to
   Lean/Rich	Lean/Rich	Normal	-	-	C
   Lean	Lean	Actual air-fuel ratio lean	May occur	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	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/Rich	A/F sensor malfunction	-	A/F sensor	B
   Rich	Lean/Rich	A/F sensor malfunction	-	A/F sensor	B

   Lean: During A/F CONTROL, 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 A/F CONTROL, the AFS is consistently less than 3.0 V, and the O2S is consistently more than 0.55 V.
   Lean/Rich: During A/F CONTROL of the ACTIVE TEST, the output voltage of the heated oxygen sensor alternates correctly.
   

B	Go to step 11
C	Go to step 15

A

1. Connect the intelligent tester to the DLC3.

2. Turn the ignition switch on and turn the tester on.

3. Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DATA LIST / PRIMARY / COOLANT TEMP.

4. Read the COOLANT TEMP twice, when the engine is cold and also when 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)
   

NG	REPLACE ENGINE COOLANT TEMPERATURE SENSOR

OK

1. Connect the intelligent tester to the DLC3.

2. Turn the ignition switch on and turn the tester on.

3. Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DATA LIST / PRIMARY / 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 2,500 rpm.

   Standard:

   MAF while engine idling:

   Between 3.2 g/s and 4.7 g/s (shift position: N, A/C: OFF).
   

   MAF at engine speed of 2,500 rpm:

   Between 13.1 g/s and 18.9 g/s (shift position: N, A/C: OFF).
   

NG	REPLACE MASS AIR FLOW METER

OK

1. Check the fuel pressure (Click here).

NG	REPAIR OR REPLACE FUEL SYSTEM

OK

OK:

No gas leakage.

NG	REPAIR OR REPLACE EXHAUST SYSTEM

OK

1. Check for sparks and ignition (Click here).

   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: DIAGNOSIS / ENHANCED OBD II / DATA LIST / PRIMARY / CYL #1 (to CYL #6).

NG	REPAIR OR REPLACE IGNITION SYSTEM

OK

1. Inspect the fuel injector assembly (Click here).

   HINT:

   If the injectors malfunction, engine misfire may occur. The misfire count can be read using the intelligent tester. Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DATA LIST / PRIMARY / CYL #1 (to CYL #6).

NG	REPLACE FUEL INJECTOR ASSEMBLY

OK

1. Disconnect the A12 or A13 A/F sensor connector.

2. Measure the resistance between the terminals of the A/F sensor connector.
   

   Standard resistance:

   Bank 1:

   Tester Connections	Specified Conditions
   HT (1) - +B (2)	1.8 to 3.4 Ω at 20°C (68°F)
   HT (1) - A1A- (4)	10 kΩ or higher

   Bank 2:

   Tester Connections	Specified Conditions
   HT (1) - +B (2)	1.8 to 3.4 Ω at 20°C (68°F)
   HT (1) - AF- (4)	10 kΩ or higher

3. Reconnect the A/F sensor connector.

NG	REPLACE AIR FUEL RATIO SENSOR

OK

1. Remove the A/F sensor heater relay from the engine room R/B.

2. Measure the A/F sensor heater relay resistance.

   Standard resistance:

   Tester Connections	Specified Conditions
   3 - 5	10 kΩ or higher
   3 - 5	Below 1 Ω (when battery voltage applied to terminals 1 and 2)

3. Reinstall the A/F sensor heater relay.

NG	REPLACE AIR FUEL RATIO SENSOR HEATER RELAY

OK

1. Disconnect the A12 or A13 A/F sensor connector.

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 Connections	Specified Conditions
   +B (A12-2) - Body ground	9 to 14 V
   +B (A13-2) - Body ground	9 to 14 V

4. Turn the ignition switch off.

5. Disconnect the E5 ECM connector.

6. Measure the resistance.

   Standard resistance (Check for open):

   Tester Connections	Specified Conditions
   HT (A12-1) - HA1A (E5-2)	Below 1 Ω
   AF+ (A12-3) - A1A+ (E5-22)	Below 1 Ω
   AF- (A12-4) - A1A- (E5-30)	Below 1 Ω
   HT (A13-1) - HA2A (E5-1)	Below 1 Ω
   AF+ (A13-3) - A2A+ (E5-23)	Below 1 Ω
   AF- (A13-4) - A2A- (E5-31)	Below 1 Ω

   Standard resistance (Check for short):

   Tester Connections	Specified Conditions
   HT (A12-1) or HA1A (E5-2) - Body ground	10 kΩ or higher
   AF+ (A12-3) or A1A+ (E5-22) - Body ground	10 kΩ or higher
   AF- (A12-4) or A1A- (E5-30) - Body ground	10 kΩ or higher
   HT (A13-1) or HA2A (E5-1) - Body ground	10 kΩ or higher
   AF+ (A13-3) or A2A+ (E5-23) - Body ground	10 kΩ or higher
   AF- (A13-4) or A2A- (E5-31) - Body ground	10 kΩ or higher

7. Reconnect the ECM connector.

8. Reconnect the A/F sensor connector.

   
   
   
   

NG	REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

NEXT

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

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

3. Clear DTCs (Click here) (Procedure C).

4. Switch the ECM from normal mode to check mode using the tester (Click here) (Procedure D).

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

6. Drive the vehicle at between 38 mph and 75 mph (60 km/h and 120 km/h) and at an engine speed of between 1,400 rpm and 3,200 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.

NEXT

1. Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / PENDING CODES.

2. Read DTCs.
   

   Result:

   
   

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

B	Go to step 5

A
END