P0171
2GR-FE ENGINE CONTROL SYSTEM: 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 time. 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 (A/F) 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 trims 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:
- 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
CONFIRMATION DRIVING PATTERN
1. Connect the Techstream to the DLC3.
2. Turn the engine 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 engine switch off and wait for 30 seconds.
5. Turn the engine switch on (IG) and turn the Techstream on [A].
6. 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 [B].
7. With the engine warmed up, idle the engine for 2 minutes or more [C].
8. Drive the vehicle at between 37 and 75 mph (60 and 120 km/h) for 5 minutes or more [D].
CAUTION:
When performing the confirmation driving pattern, obey all speed limits and traffic laws.
9. Enter the following menus: Powertrain / Engine / Trouble Codes / Pending.
10. Read the pending DTC [E].
11. If a pending DTC is output, the system is malfunctioning.
HINT
If a pending DTC is not output, perform the following procedure.
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 P2195 P2195.
Refer to DTC P0102 P0102.
INSPECTION PROCEDURE
HINT
For use of the Techstream only:
Malfunctioning areas can be identified by performing the Control the Injection Volume for A/F Sensor function provided in the Active Test. The Control the Injection Volume for A/F Sensor 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 Control the Injection Volume for A/F Sensor operation using the Techstream.
1. Connect the Techstream to the DLC3.
2. Start the engine and turn the Techstream on.
3. Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
4. Select the following menu items on the Techstream: Powertrain / Engine / 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 voltage outputs of the A/F and HO2 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.
Standard voltage:
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.
- Following the Control the Injection Volume for A/F Sensor procedure enables technicians to check and graph the voltage outputs of both the A/F and HO2 sensors.
- To display the graph, select the following menu items on the Techstream: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor /AFS Voltage B1S1 or AFS Voltage B2S1 and O2S B1S2 or O2S B2S2 then press the graph button on the Data List view.
NOTICE:
Inspect the fuses of circuits related to this system before performing the following inspection procedure.
HINT
- 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.
- 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.
- Bank 1 refers to the bank that includes the No. 1 cylinder*.
- *: The No. 1 cylinder is the cylinder which is farthest from the transaxle.
- 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.
- 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 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.
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 engine switch on (IG) and turn the Techstream on.
(c) Enter the following menus: Powertrain / Engine / Trouble Codes.
(d) 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 On-Vehicle Inspection.
OK:
PCV hose is connected correctly and is not damaged.
NG -- REPAIR OR REPLACE PCV HOSE
OK -- Continue to next step.
3. CHECK AIR INDUCTION SYSTEM
(a) Check the air induction system for vacuum leaks.
OK:
No leaks in air induction system.
NG -- REPAIR OR REPLACE AIR INDUCTION SYSTEM
OK -- Continue to next step.
4. PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE INJECTION VOLUME)
(a) Connect the Techstream to the DLC3.
(b) Start the engine and turn the Techstream on.
(c) Warm up the engine and run the engine at an engine speed of 2500 rpm for approximately 90 seconds.
(d) 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.
(e) Perform the Control the Injection Volume operation with the engine idling.
(f) Monitor the output voltages of the A/F and HO2 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.
Standard voltage:
Result:
Lean: During Control the Injection Volume the A/F sensor output voltage (AFS) is consistently more than 3.4 V, and the HO2 sensor output voltage (O2S) is consistently less than 0.4 V.
Rich: During Control the Injection Volume the AFS is consistently less than 3.1 V, and the O2S is consistently more 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, VFS 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 engine switch on (IG) and turn the Techstream on.
(c) Enter the following menus: Powertrain / Engine / Data List / Coolant Temp.
(d) 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) Start the engine.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine / Data List / All Data / MAF and Coolant Temp.
(e) Allow the engine to idle until Coolant Temp reaches 75°C (167°F) or higher.
(f) Read MAF with the engine speed at 2500 rpm.
Standard:
Between 8 g/sec. and 19 g/sec. (shift lever: N; A/C: Off).
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.
Result:
B -- CHECK WHETHER DTC OUTPUT RECURS (DTC P0171, P0172, P0174 OR P0175)
A -- REPLACE FUEL INJECTOR ASSEMBLY Removal
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 A/F SENSOR) P0031
NG -- INSPECT ENGINE ROOM JUNCTION BLOCK (A/F RELAY)
OK -- Continue to next step.
13. CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM)
(a) Disconnect the B3 and B4 A/F sensor connectors.
(b) Disconnect the B12 ECM 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 ECM connector.
(e) Reconnect the A/F sensor 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, P0172, P0174 OR P0175)
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG) and turn the Techstream on.
(c) Clear the DTCs Reading and Clearing Diagnostic Trouble Codes.
(d) Turn the engine switch off.
(e) Turn the engine switch on (IG) and turn the Techstream on.
(f) Start the engine and warm it up.
(g) Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
(h) Enter the following menus: Powertrain / Engine / Trouble Codes.
(i) Read the pending DTCs.
Result:
B -- END
A -- Continue to next step.
16. CHECK HARNESS AND CONNECTOR
(a) Check the connection and terminal contact pressure of connectors and wire harnesses between the mass air flow meter and ECM Electronic Circuit Inspection Procedure.
HINT
Repair any problems.
NEXT -- Continue to next step.
17. CHECK WHETHER DTC OUTPUT RECURS (DTC P0171, P0172, P0174 OR P0175)
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG) and turn the Techstream on.
(c) Clear the DTCs Reading and Clearing Diagnostic Trouble Codes.
(d) Turn the engine switch off.
(e) Turn the engine switch on (IG) and turn the Techstream on.
(f) Start the engine and warm it up.
(g) Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
(h) Enter the following menus: Powertrain / Engine / Trouble Codes.
(i) Read the pending DTCs.
Result:
B -- END
A -- Continue to next step.
18. CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER - ECM)
(a) Disconnect the B33 MAF meter connector.
(b) Disconnect the B12 ECM connector.
(c) Measure the resistance between the terminals.
Standard resistance (Check for open):
Standard resistance (Check for short):
(d) Reconnect the MAF meter connector.
(e) Reconnect the ECM connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
19. REPLACE MASS AIR FLOW METER SUB- ASSEMBLY
(a) Replace the mass air flow meter 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 assembly.
NEXT -- Continue to next step.
20. CONFIRM CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG) and turn the Techstream on.
(c) Clear the DTCs Reading and Clearing Diagnostic Trouble Codes.
(d) Turn the engine switch off.
(e) Turn the engine switch on (IG) and turn the Techstream on.
(f) Start the engine and warm it up.
(g) Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
(h) Enter the following menus: Powertrain / Engine / Trouble Codes / Pending.
(i) Read the pending DTCs.
Result:
B -- END
A -- REPLACE ECM Removal
21. INSPECT ENGINE ROOM JUNCTION BLOCK (A/F RELAY)
(a) Inspect the engine room junction block Testing and Inspection.
NG -- REPLACE ENGINE ROOM JUNCTION BLOCK
OK -- REPAIR OR REPLACE HARNESS OR CONNECTOR (AIR FUEL RATIO SENSOR - ENGINE ROOM JUNCTION BLOCK)