P0172

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

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 trims.

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 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 trims are lean or rich beyond predetermined values, it is interpreted as a malfunction, and the hybrid vehicle control ECU illuminates the MIL and stores a DTC.





HINT
- When DTC P0171 is stored, the actual air fuel ratio is on the lean side. When DTC P0172 is stored, 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 may be stored. 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 higher 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 hybrid vehicle control ECU 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 fuel injection volumes estimated by the hybrid vehicle control ECU also affect the average fuel trim learned value, which is a combination of the average short-term fuel trim (fuel feedback compensation value) and the average long-term fuel trim (learned value of the air fuel ratio). If the average fuel trim learned value exceeds the malfunction thresholds, the hybrid vehicle control ECU interprets this as a fault in the fuel system and stores a DTC.

Example:

The average fuel trim learned value is 35% or more, or -35% or less, the hybrid vehicle control ECU interprets this as a fuel system malfunction.





MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS





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) Reading and Clearing Diagnostic Trouble Codes.

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

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

6. Put the engine in inspection mode (maintenance 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 higher with all the accessories switched off.

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

9. Drive the vehicle at a speed between 75 and 120 km/h (47 and 75 mph) for 5 minutes or more.

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

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

11. Read pending DTCs.

HINT
If a pending DTC is output, the system is malfunctioning.

12. If no pending DTC is output, 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 P0102 P0102.

Refer to DTC P2195 P2195.

INSPECTION PROCEDURE

HINT
Malfunctioning areas can be identified by performing the Control the Injection Volume function provided in the Active Test. The Control the Injection Volume 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 operation using the Techstream.

(a) Connect the Techstream to the DLC3.
(b) Turn the Techstream on.
(c) Put the engine in inspection mode (maintenance mode) Component Tests and General Diagnostics.
(d) Start the engine.
(e) Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
HINT
During charging control, the engine speed is set at idle. Therefore, the engine speed does not increase when depressing the accelerator pedal. In this case, warm up the engine after charging control has completed.

(f) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume / AFS Voltage B1S1 and O2S B1S2.
(g) Perform the Active Test operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume).
(h) Monitor the output voltages of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2) displayed on the Techstream.

HINT
- Change the fuel injection volume within the range of -12% to +12%. The injection volume can be changed in fine gradations.
- 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 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 / AFS Voltage B1S1 and O2S B1S2; and then press the graph button on the Data List view.

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 hybrid vehicle control ECU 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.

PROCEDURE

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

(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 DTCs.

Result





HINT
If any DTCs other than P0171 or P0172 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 Components.

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 from 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 Techstream on.

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

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

HINT
During charging control, the engine speed is set at idle. Therefore, the engine speed does not increase when depressing the accelerator pedal. In this case, warm up the engine after charging control has completed.

(e) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume / AFS Voltage B1S1 and O2S B1S2.

(f) Perform the Control the Injection Volume operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume).

(g) Monitor the voltage outputs of the air fuel ratio sensor and the heated oxygen sensor (AFS Voltage B1S1 and O2S B1S2) displayed on the Techstream.

HINT
- Change the fuel injection volume within the range of -12% to +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:





Result





Lean: During Control the Injection Volume, the air fuel ratio sensor output voltage (AFS Voltage B1S1) is consistently higher than 3.4 V, and the heated oxygen sensor output voltage (O2S B1S2) is consistently below 0.4 V.

Rich: During Control the Injection Volume, the AFS Voltage B1S1 is consistently below 3.1 V, and the O2S B1S2 is consistently higher than 0.55 V.

Lean/Rich: During Control the Injection Volume of the Active Test, the output voltage of the heated oxygen sensor alternates correctly.

HINT
Refer to "Data List / Active Test" [AFS Voltage B1S1 and O2S B1S2] Data List / Active List.

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 / All Data / Coolant Temp.

(e) Read the Data List twice, when the engine is both cold and warmed up.

Standard:





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 (maintenance mode) Component Tests and General Diagnostics.

(e) Start the engine.

(f) Enter the following menus: Powertrain / Engine and ETC / Data List / All Data / MAF, Coolant Temp and Engine Speed.

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

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

HINT
During charging control, the engine speed is set at idle. Therefore, the engine speed does not increase when depressing the accelerator pedal. In this case, read the Data List after charging control has completed.

Standard:





NG -- CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER CONNECTOR CONNECTION)
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 SPARK (SPARK TEST)

(a) Perform a spark test Testing and Inspection.

HINT
- If the result of the spark test is normal, proceed to the next step.
- If the spark plugs or ignition system malfunctions, engine misfire may occur. The misfire count can be read using the Techstream. Enter the following menus: Powertrain / Engine and ECT / Data List / Gas Misfire / Cylinder #1 Misfire Count (to Cylinder #4 Misfire Count).

NEXT -- Continue to next step.

10. INSPECT FUEL INJECTOR ASSEMBLY (INJECTION AND VOLUME)

HINT
- Refer to the fuel injector assembly inspection procedure Testing and Inspection.
- If the injectors malfunction, engine misfire may occur. The misfire count can be read using the Techstream. Enter the following menus: Powertrain / Engine and ETC / Data List / Gas Misfire / Cylinder #1 Misfire Count (to Cylinder #4 Misfire Count).

OK -- CHECK WHETHER DTC OUTPUT RECURS (DTC P0171 OR P0172)

NG -- REPLACE FUEL INJECTOR ASSEMBLY Removal

11. INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

(a) Inspect the air fuel ratio sensor Air Fuel Ratio Sensor.

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

12. CHECK TERMINAL VOLTAGE (POWER SOURCE OF AIR FUEL RATIO SENSOR) P0031

NG -- INSPECT NO. 1 INTEGRATION RELAY (EFI MAIN RELAY)
OK -- Continue to next step.

13. CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - HYBRID VEHICLE CONTROL ECU)

(a) Disconnect the air fuel ratio sensor connector.

(b) Disconnect the hybrid vehicle control ECU connector.

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

Standard Resistance (Check for Open):





Standard Resistance (Check for Short):





(d) Reconnect the air fuel ratio sensor connector.

(e) Reconnect the hybrid vehicle control ECU connector.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
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. CHECK WHETHER DTC OUTPUT RECURS (DTC P0171 OR P0172)

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

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

(g) Read DTCs.

Result





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

16. CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER CONNECTOR CONNECTION)

(a) Check the connection and terminal contact pressure of connectors and wire harnesses between the mass air flow meter and hybrid vehicle control ECU Electronic Circuit Inspection Procedure.

HINT
Repair any problems.

NEXT -- Continue to next step.

17. CHECK WHETHER DTC OUTPUT RECURS (DTC P0171 OR P0172)

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

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

(g) Read DTCs.

Result





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

18. CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER - HYBRID VEHICLE CONTROL ECU) P0102

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

19. REPLACE MASS AIR FLOW METER

(a) Replace the mass air flow meter 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 -- Continue to next step.

20. 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 DTCs Reading and Clearing Diagnostic Trouble Codes.

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

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

(g) Read DTCs.

Result





B -- REPLACE HYBRID VEHICLE CONTROL ECU Removal

A -- END

21. INSPECT NO. 1 INTEGRATION RELAY (EFI MAIN RELAY)

(a) Inspect the No. 1 integration relay Inspection.

NG -- REPLACE NO. 1 INTEGRATION RELAY
OK -- Continue to next step.

22. CHECK HARNESS AND CONNECTOR (EFI MAIN RELAY - AIR FUEL RATIO SENSOR) P0031

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

23. CHECK HARNESS AND CONNECTOR (EFI MAIN RELAY - IGCT RELAY) P0031

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

24. CHECK HARNESS AND CONNECTOR (EFI MAIN RELAY - BODY GROUND) P0031

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPAIR OR REPLACE HARNESS OR CONNECTOR (AUXILIARY BATTERY - EFI MAIN RELAY)