P0171

2GR-FXE ENGINE CONTROL: SFI SYSTEM: P0171,P0172,P0174,P0175: System Too Lean (Bank 1)
P0175 - System Too Rich (Bank 2)

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.

If both the short-term and long-term fuel trim are lean or rich beyond predetermined values, it is interpreted as a malfunction, and the ECM illuminates the MIL and sets a DTC.





HINT
- 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.
- 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.
- 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, fuel injection volumes that deviate from those 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 values. Deviations from the ECM's estimated fuel injection volumes also affect 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 the malfunction thresholds, the ECM interprets this as a fault in the fuel system and sets a DTC.

Example:

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





MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS

Fuel Trim





TYPICAL MALFUNCTION THRESHOLDS

Fuel Trim





CONFIRMATION DRIVING PATTERN





1. Connect the Techstream to the DLC3.

2. Turn the power switch on (IG) and turn the Techstream on.

3. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).

4. Turn the power switch off and wait for 30 seconds.

5. Turn the power switch on (IG) and turn the Techstream on [A].

6. Put the engine in inspection mode Component Tests and General Diagnostics.

7. Start the engine and warm it up (until the engine coolant temperature is 75°C (167°F) or more) with all the accessories switched off [B].

8. With the engine warmed up, idle the engine for 2 minutes or more [C].

9. Drive the vehicle at between 47 mph and 75 mph (75 km/h and 120 km/h) and at an engine speed of between 1400 rpm and 2500 rpm for 5 minutes or more [D].

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

11. Read the pending DTC [E].

HINT
- If a pending DTC is output, the system is malfunctioning.
- If a pending DTC is not output, perform the following procedure.

12. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

13. Input the DTC: P0171, P0172, P0174 or P0175.

14. Check the DTC judgment result.





CAUTION:
When performing the confirmation driving pattern, obey all speed limits and traffic laws.

HINT
- If the judgment result shows NORMAL, the system is normal.
- If the judgment result shows ABNORMAL, the system has a malfunction.
- If the judgment result shows INCOMPLETE or UNKNOWN, perform step [C] again.

15. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

16. Check the judgment result.

HINT
- If the judgment result shows NORMAL, the system is normal.
- If the judgment result shows ABNORMAL, the system has a malfunction.

17. If the test result is INCOMPLETE or UNKNOWN, perform a universal trip and check for permanent DTCs Reading and Clearing Diagnostic Trouble Codes.

HINT
- If a permanent DTC is output, the system is malfunctioning.
- If no permanent DTC is output, the system is normal.

WIRING DIAGRAM

Refer to DTC P2195 P2195.

INSPECTION PROCEDURE

HINT
Malfunctioning areas can be identified by performing the Control the Injection Volume for A/F Sensor in the Active Test. The Control the Injection Volume for A/F Sensor function can help to determine whether the air fuel ratio sensor, heated oxygen 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 Techstream.

1. Connect the Techstream to the DLC3.

2. Turn the power switch on (IG).

3. Turn the Techstream on.

4. Put the engine in inspection mode Component Tests and General Diagnostics.

5. Start the engine.

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

7. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.

8. Perform the Active Test operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume).

9. Monitor the voltage outputs of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2) displayed on the Techstream.

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 and decreases in the fuel injection volume.





NOTICE:
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.





- Following the Control the Injection Volume for A/F Sensor procedure enables technicians to check and graph the voltage outputs of both the air fuel ratio and heated oxygen sensors.

- To display the graph, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2.

NOTICE:
Inspect the fuses for circuits related to this system before performing the following inspection procedure.

HINT
- 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 help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air fuel ratio was lean or rich, and other data from the time the malfunction occurred.
- 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.
- 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.
- Bank 1 refers to the bank that includes the No. 1 cylinder*.
*: The No. 1 cylinder is the cylinder which is farthest from the transmission.
- Bank 2 refers to the bank that does not include the No. 1 cylinder.
- Sensor 1 refers to the sensor closest to the engine assembly.
- Sensor 2 refers to the sensor farthest away from the engine assembly.

PROCEDURE

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

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

(e) Read the DTCs.

Result:





HINT
If any DTCs other than P0171, P0172, P0174 or P0175 are output, troubleshoot those DTCs first.

B -- GO TO DTC CHART SFI System
A -- Continue to next step.

2. CHECK PCV HOSE CONNECTIONS

(a) Check the PCV hose connections Testing and Inspection.

OK:

PCV hose is connected correctly and is not damaged.

NG -- REPAIR OR REPLACE PCV HOSE
OK -- Continue to next step.

3. CHECK INTAKE SYSTEM

(a) Check the intake system for vacuum leaks Intake System.

OK:

No leaks in intake system.

NG -- REPAIR OR REPLACE INTAKE SYSTEM
OK -- Continue to next step.

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

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Put the engine in inspection mode Component Tests and General Diagnostics.

(e) Start the engine.

(f) Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.

(g) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume.

(h) Perform the Control the Injection Volume operation with the engine idling.

(i) Monitor the output voltages of the air fuel ratio and heated oxygen sensors (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 -12.0% to +12.0%. 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.





Result:





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, AFS Voltage B2S1, O2S B1S2 and O2S B2S2] Data List / Active Test.

B -- INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)
A -- Continue to next step.

5. READ VALUE USING TECHSTREAM (COOLANT TEMP)

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine and ECT / Data List / Coolant Temp.

(e) 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 -- REPLACE ENGINE COOLANT TEMPERATURE SENSOR Removal
OK -- Continue to next step.

6. READ VALUE USING TECHSTREAM (MAF)

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Put the engine in inspection mode Component Tests and General Diagnostics.

(e) Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / MAF and Coolant Temp.

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

(g) Read MAF with the engine speed at 2500 rpm.

Standard:

Between 6 gm/sec and 17 gm/sec (shift lever: P).

HINT
When the vehicle is stopped, the engine is being raced with the accelerator pedal depressed 60% or more

NG -- CHECK HARNESS AND CONNECTOR
OK -- Continue to next step.

7. CHECK FUEL PRESSURE

(a) Check the fuel pressure Fuel System.

NG -- REPAIR OR REPLACE FUEL SYSTEM
OK -- Continue to next step.

8. CHECK FOR EXHAUST GAS LEAK

(a) Check for exhaust gas leaks.

OK:

No gas leaks

NG -- REPAIR OR REPLACE EXHAUST SYSTEM
OK -- Continue to next step.

9. CHECK FOR SPARKS AND IGNITION P0300

NG -- REPAIR OR REPLACE IGNITION SYSTEM
OK -- Continue to next step.

10. INSPECT FUEL INJECTOR ASSEMBLY (INJECTION AND VOLUME)

(a) Check the injection and volume Testing and Inspection.

NG -- REPLACE FUEL INJECTOR ASSEMBLY Removal

OK -- PERFORM CONFIRMATION DRIVING PATTERN

11. INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE) P0031

NG -- REPLACE AIR FUEL RATIO SENSOR Removal
OK -- Continue to next step.

12. CHECK TERMINAL VOLTAGE (+B OF AIR FUEL RATIO SENSOR) P0031

NG -- CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ENGINE ROOM JUNCTION BLOCK ASSEMBLY)
OK -- Continue to next step.

13. CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM) P2237

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (AIR FUEL RATIO SENSOR - ECM)
OK -- Continue to next step.

14. REPLACE AIR FUEL RATIO SENSOR

(a) Replace the air fuel ratio sensor Removal.

NEXT -- Continue to next step.

15. PERFORM CONFIRMATION DRIVING PATTERN

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Clear the DTCs Reading and Clearing Diagnostic Trouble Codes.

(e) Turn the power switch off.

(f) Turn the power switch on (IG) and turn the Techstream on.

(g) Put the engine in inspection mode Component Tests and General Diagnostics.

(h) Start the engine and warm it up.

(i) Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.

(j) Enter the following menus: Powertrain / Engine and ECT / Utility / Trouble Codes / Pending.

(k) Read the pending DTCs.

Result:





B -- END
A -- Continue to next step.

16. PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE EGR STEP POSITION)

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Put the engine in inspection mode Component Tests and General Diagnostics.

(e) Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or more.

HINT
The A/C switch and all accessory switches should be off.

(f) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position.

(g) Confirm the Throttle Idle Position is ON and check the engine idling condition and MAP values in the Data List while performing the Active Test.

HINT
- Do not leave the EGR valve open for 10 seconds or more during the Active Test.
- Be sure to return the EGR valve to step 0 when Active Test is completed.

OK:

MAP and idling condition change in response to EGR step position as follows.

Standard:





HINT
During Active Test, if the idling condition does not change in response to EGR step position, then there is probably a malfunction in EGR valve.

NG -- INSPECT EGR VALVE ASSEMBLY

OK -- CHECK HARNESS AND CONNECTOR

17. INSPECT EGR VALVE ASSEMBLY

(a) Remove the EGR valve assembly Removal.

(b) Check if the EGR valve is stuck open.

OK:

EGR valve is tightly closed.

(c) Reinstall the EGR valve assembly Installation.

NG -- REPLACE EGR VALVE ASSEMBLY Removal
OK -- Continue to next step.

18. CHECK HARNESS AND CONNECTOR

(a) Check the connection and terminal contact pressure of connectors and wire harnesses between the mass air flow meter sub-assembly and ECM Electronic Circuit Inspection Procedure.

HINT
Repair any problems.

NEXT -- Continue to next step.

19. CHECK WHETHER DTC OUTPUT RECURS

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Clear the DTCs Reading and Clearing Diagnostic Trouble Codes.

(e) Turn the power switch off.

(f) Turn the power switch on (IG) and turn the Techstream on.

(g) Put the engine in inspection mode Component Tests and General Diagnostics.

(h) Start the engine and warm it up.

(i) Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.

(j) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Pending.

(k) Read the pending DTCs.

Result





B -- END
A -- Continue to next step.

20. CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER SUB-ASSEMBLY - ECM)

(a) Disconnect the mass air flow meter sub-assembly connector.

(b) Disconnect the ECM connector.

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

Standard Resistance:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

21. REPLACE MASS AIR FLOW METER SUB-ASSEMBLY

(a) Replace the mass air flow meter sub-assembly 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 sub-assembly.

NEXT -- Continue to next step.

22. CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Clear the DTC Reading and Clearing Diagnostic Trouble Codes.

(e) Turn the power switch off.

(f) Turn the power switch on (IG) and turn the Techstream on.

(g) Put the engine in inspection mode Component Tests and General Diagnostics.

(h) Start the engine and warm it up.

(i) Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.

(j) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Pending.

(k) Read the pending DTCs.

Result





B -- REPLACE ECM Removal

A -- END

23. CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ENGINE ROOM JUNCTION BLOCK ASSEMBLY) P0031

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (AIR FUEL RATIO SENSOR - ENGINE ROOM JUNCTION BLOCK ASSEMBLY)
OK -- Continue to next step.

24. CHECK TERMINAL VOLTAGE (ENGINE ROOM JUNCTION BLOCK ASSEMBLY) P0031

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (ENGINE ROOM JUNCTION BLOCK ASSEMBLY - BATTERY)
OK -- Continue to next step.

25. CHECK HARNESS AND CONNECTOR (ENGINE ROOM JUNCTION BLOCK ASSEMBLY - EFI MAIN RELAY) P0031

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (ENGINE ROOM JUNCTION BLOCK ASSEMBLY - EFI MAIN RELAY)
OK -- Continue to next step.

26. CHECK HARNESS AND CONNECTOR (ENGINE ROOM JUNCTION BLOCK ASSEMBLY - BODY GROUND) P0031

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (ENGINE ROOM JUNCTION BLOCK ASSEMBLY - BODY GROUND)

OK -- REPLACE ENGINE ROOM JUNCTION BLOCK ASSEMBLY