P0171
4GR-FSE 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 then illuminates.
- 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 more than +35% or less than -35%, the ECM interprets this as a fuel system malfunction.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
Fuel Trim
TYPICAL MALFUNCTION THRESHOLDS
Fuel Trim
CONFIRMATION DRIVING PATTERN
- Connect the Techstream to the DLC3.
- Turn the engine switch on (IG) and turn the Techstream on.
- Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure) DTC Check / Clear.
- Turn the engine switch off.
- Turn the engine switch on (IG) and turn the Techstream on [A].
- 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].
- With the engine warmed up, idle the engine for 2 minutes or more [C].
- Drive the vehicle at between 37 mph and 75 mph (60 km/h and 120 km/h) and at an engine speed of between 1400 rpm and 3200 rpm for 5 minutes or more [D].
- Enter the following menus: Powertrain / Engine / Utility / All Readiness.
- Input the DTC: P0171, P0172, P0174 or P0175.
- Check the DTC judgment result [E].
CAUTION:
When performing the confirmation driving pattern, obey all speed limits and traffic laws.
HINT
- If the judgment result shows ABNORMAL, the system has a malfunction.
- If the judgment result shows INCOMPLETE or UNKNOWN, perform steps [C] through [E] again.
- If the test result is UNKNOWN, enter the following menus: Powertrain / Engine / Trouble Codes / Pending.
- Read Pending DTCs.
HINT
If a pending DTC is output, the system is malfunctioning.
- If the test result is INCOMPLETE or UNKNOWN and no pending DTC is output, perform a universal trip and check for permanent DTCs DTC Check / Clear.
HINT
- If a permanent DTC is output, the system is malfunctioning.
- If no permanent DTC is output, the system is normal.
WIRING DIAGRAM
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.
- Connect the Techstream to the DLC3.
- Start the engine.
- Turn the Techstream on.
- Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
- Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor.
- Perform the Active Test operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume).
- 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 / 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.
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).
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine / 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 (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 Testing and Inspection.
OK:
No leaks in the intake system.
NG -- REPAIR OR REPLACE INTAKE SYSTEM
OK -- Continue to next step.
4. PERFORM ACTIVE TEST USING TECHSTREAM (AIR FUEL RATIO CONTROL)
(a) Connect the Techstream to the DLC3.
(b) Start the engine.
(c) Turn the Techstream on.
(d) Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
(e) Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor.
(f) Perform the Active Test operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume).
(g) 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
- 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.
Result:
(h) 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.
C -- PERFORM CONFIRMATION DRIVING PATTERN
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).
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine / Data List / Coolant Temp.
(e) Read the Data List 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 95°C (167°F and 203°F)
NG -- REPLACE ENGINE COOLANT TEMPERATURE SENSOR
OK -- Continue to next step.
6. INSPECT MASS AIR FLOW METER
(a) Inspect the mass air flow meter P0102.
NG -- REPLACE MASS AIR FLOW METER Removal
OK -- Continue to next step.
7. CHECK FUEL PRESSURE (LOW PRESSURE SIDE)
(a) Check the fuel pressure (low pressure side) Testing and Inspection.
NG -- REPAIR OR REPLACE FUEL SYSTEM (LOW PRESSURE SIDE)
OK -- Continue to next step.
8. CHECK FUEL PRESSURE SENSOR
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG) and turn the Techstream on.
(c) Start the engine.
(d) Enter the following menus: Powertrain / Engine / Data List / Fuel Press.
(e) While revving the engine, check that the fuel pressure fluctuates.
OK:
Fuel pressure fluctuates.
NG -- REPLACE FUEL PRESSURE SENSOR
OK -- Continue to next step.
9. CHECK FUEL PRESSURE (HIGH PRESSURE SIDE)
(a) Check the fuel pressure (high pressure side) Testing and Inspection.
NG -- REPAIR OR REPLACE FUEL SYSTEM (HIGH PRESSURE SIDE)
OK -- Continue to next step.
10. INSPECT FOR EXHAUST GAS LEAK
(a) Inspect for exhaust gas leaks from the exhaust manifold sub-assembly and exhaust pipes.
OK:
No gas leaks
NG -- REPAIR OR REPLACE EXHAUST GAS LEAK POINT
OK -- Continue to next step.
11. CHECK IGNITION SYSTEM
(a) Check the ignition system Testing and Inspection.
NG -- REPAIR OR REPLACE IGNITION SYSTEM
OK -- Continue to next step.
12. INSPECT FUEL INJECTOR ASSEMBLY
(a) Inspect the fuel injector assembly Testing and Inspection.
(b) Inspect the cold start injector Testing and Inspection.
NG -- REPLACE FUEL INJECTOR ASSEMBLY Removal
OK -- Continue to next step.
13. INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE) P0031
NG -- REPLACE AIR FUEL RATIO SENSOR Removal
OK -- Continue to next step.
14. CHECK TERMINAL VOLTAGE (+B TERMINAL OF AIR FUEL RATIO SENSOR) P0031
NG -- INSPECT RELAY (A/F RELAY)
OK -- Continue to next step.
15. CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM)
(a) Disconnect the air fuel ratio sensor connector.
(b) Disconnect the 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):
Text in Illustration
(d) Reconnect the ECM connector.
(e) Reconnect the air fuel ratio sensor connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
16. REPLACE AIR FUEL RATIO SENSOR
(a) Replace the air fuel ratio sensor Removal.
NEXT -- Continue to next step.
17. PERFORM CONFIRMATION DRIVING PATTERN
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Turn the Techstream on.
(d) Clear the DTCs DTC Check / Clear.
(e) Turn the engine switch off.
(f) Turn the engine switch on (IG) and turn the Techstream on.
(g) Start the engine and warm it up.
(h) Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
(i) Enter the following menus: Powertrain / Engine / Utility / All Readiness.
(j) Input the DTC: P0171, P0172, P0174 or P0175.
(k) Check the DTC judgment result.
Result:
B -- REPLACE ECM Removal
A -- END
18. INSPECT RELAY (A/F RELAY) P0031
NG -- REPLACE RELAY (A/F RELAY)
OK -- Continue to next step.
19. CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - A/F RELAY) P0031
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
20. CHECK TERMINAL VOLTAGE (A/F RELAY) P0031
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
21. CHECK HARNESS AND CONNECTOR (A/F RELAY - BODY GROUND) P0031
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPAIR OR REPLACE HARNESS OR CONNECTOR (EFI MAIN RELAY - A/F RELAY)
1. PERFORM CONFIRMATION DRIVING PATTERN
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Turn the Techstream on.
(d) Clear the DTCs DTC Check / Clear.
(e) Turn the engine switch off.
(f) Turn the engine switch on (IG) and turn the Techstream on.
(g) Start the engine and warm it up.
(h) Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
(i) Enter the following menus: Powertrain / Engine / Utility / All Readiness.
(j) Input the DTC: P0171, P0172, P0174 or P0175.
(k) Check the DTC judgment result.
Result:
B -- REPLACE ECM Removal
A -- CHECK FOR INTERMITTENT PROBLEMS