P0175
2GR-FSE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0171: System Too Lean (Bank 1)
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
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 the 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 (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 ideal theoretical value. The long-term fuel trim controls overall fuel compensation. The long-term fuel trim compensates for long term deviations of the fuel trim from the ideal theoretical value. These long term deviations result from the corrections made by the short-term fuel trim.
If both the short-term fuel 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 (2 trip detection logic).
HINT: 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.
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 threshold, the ECM interprets this as a fault in the fuel system and sets a DTC.
- Example:
If 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
TYPICAL MALFUNCTION THRESHOLDS
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT: 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 Put the engine in inspection mode Inspection Mode Procedure.
2 Connect the Techstream.
3 Turn the Techstream on.
4 Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
5 Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F sensor.
6 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 injection volume).
7 Monitor the output voltages of the A/F and HO2 sensors (AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2) displayed on the Techstream.
HINT:
- The Control the Injection Volume for A/F sensor operation lowers the injection volume by 12.5% or increases the injection volume by 25%.
- Each sensor reacts in accordance with increases and decreases in the injection volume.
NOTE: 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 A/F CONTROL procedure enables technicians to check and graph the voltage outputs of both the A/F and HO2 sensors.
- To display the graph, enter the following menus: Powertrain / Engine and ECT / Data List / Control the Injection Volume for A/F sensor / AFS B1 S1 or AFS B2 S1 and O2S B1 S1 or O2S B2 S2; then press the graph button on the Data List view.
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 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 Freeze Frame Data.
- 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 rich 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) Put the engine in inspection mode Inspection Mode Procedure.
(b) Connect the Techstream to the DLC3.
(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
A -- Continue to next step.
2. PERFORM SYSTEM CHECK (D-4S TEST)
(a) Put the engine in inspection mode Inspection Mode Procedure.
(b) Connect the Techstream to the DLC3.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Way / Port.
(e) Read the value Short #1 and Long FT #1 and/or Short FT #2 and Long FT #2.
OK:
Short FT #1(#2) + Long FT #1(#2) = Between -19% and +19%
(f) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Way / Direct.
(g) Read the value Short FT #1 and Long FT #1 and/or Short FT #2 and Long FT #2.
OK:
Short FT #1(#2) + Long FT #1(#2) = Between -19% and +19%
Result:
C -- CHECK FUEL INJECTOR FOR PORT INJECTION
B -- CHECK FUEL PRESSURE SENSOR
A -- CHECK FOR INTERMITTENT PROBLEMS
D -- Continue to next step.
3. CHECK VENTILATION HOSE
OK:
Ventilation hose is connected correctly and is not damaged.
NG -- REPAIR OR REPLACE VENTILATION HOSE
OK -- Continue to next step.
4. CHECK AIR INDUCTION SYSTEM
(a) Check the air induction system for vacuum leakage.
OK:
No leakage from air induction system.
NG -- REPAIR OR REPLACE AIR INDUCTION SYSTEM
OK -- Continue to next step.
5. PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE INJECTION VOLUME FOR A/F SENSOR)
(a) Put the engine in inspection mode Inspection Mode Procedure.
(b) Connect the Techstream to the DLC3.
(c) Turn Techstream on.
(d) Warm up the engine.
(e) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F sensor.
(f) 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).
(g) Monitor the output voltages of the A/F and HO2 sensors (AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2) 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:
- Lean:
During Control the Injection Volume for A/F sensor, 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 Control the Injection Volume for A/F sensor, the AFS is consistently less than 3.0 V, and the O2S is consistently more than 0.55 V.
B -- INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)
A -- Continue to next step.
6. READ VALUE USING TECHSTREAM (COOLANT TEMP)
(a) Put the engine in inspection mode Inspection Mode Procedure.
(b) Connect the Techstream to the DLC3.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Data List / Coolant Temp.
(e) Read the 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 and 95°C (167 and 203°F)
NG -- REPLACE ENGINE COOLANT TEMPERATURE SENSOR
OK -- Continue to next step.
7. INSPECT MASS AIR FLOW METER SUB-ASSEMBLY
(a) Inspect the mass air flow meter sub-assembly.
NG -- REPLACE MASS AIR FLOW METER
OK -- Continue to next step.
8. CHECK FOR EXHAUST GAS LEAK
OK:
No gas leakage.
NG -- REPAIR OR REPLACE EXHAUST SYSTEM
OK -- Continue to next step.
9. INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE) P0031
NG -- REPLACE AIR FUEL RATIO SENSOR
OK -- Continue to next step.
10. INSPECT INTEGRATION RELAY (A/F RELAY) P0031
NG -- REPLACE INTEGRATION RELAY
OK -- Continue to next step.
11. CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM) P0031
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
12. REPLACE AIR FUEL RATIO SENSOR
NEXT -- Continue to next step.
13. PERFORM CONFIRMATION DRIVING PATTERN
(a) Connect the Techstream to the DLC3.
(b) Turn the power switch on (IG) and turn the Techstream on.
(c) Clear DTCs DTC Check / Clear.
(d) Switch the ECM from normal mode to check mode using the Techstream Check Mode Procedure.
(e) Start the engine and warm it up with all the accessories switched off. (Procedure "A")
(f) 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 "B")
HINT: If the system is still malfunctioning, the MIL will be illuminated during procedure "B".
NOTE: If the conditions in this test are not strictly followed, no malfunction will be detected.
NEXT -- Continue to next step.
14. CHECK WHETHER DTC OUTPUT RECURS (DTC P0171, P0172, P0174 OR P0175)
(a) On the Techstream, enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
(b) Read the DTCs.
Result:
A -- END
B -- Continue to next step.
15. CHECK FUEL PRESSURE (LOW PRESSURE)
(a) Check the fuel pressure Testing and Inspection.
OK -- REPLACE ECM
NG -- Continue to next step.
16. CHECK FUEL PUMP OPERATION
(a) Check the fuel pump operation Testing and Inspection.
NG -- REPLACE FUEL PUMP
OK -- Continue to next step.
17. CHECK FUEL LEAK (LOW PRESSURE SIDE)
OK:
No leakage
NG -- REPAIR OR REPLACE FUEL SYSTEM
OK -- CHECK AND REPLACE FUEL PUMP, PRESSURE REGULATOR, FUEL PIPE LINE AND FILTER
18. CHECK FUEL PRESSURE SENSOR
(a) Put the engine in inspection mode Inspection Mode Procedure.
(b) Connect the Techstream to the DLC3.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Fuel Press.
(e) While revving the engine, check that the fuel pressure fluctuates.
Standard:
Idling
3 to 5 MPa
2,500 rpm (Depress accelerator pedal fully)
7 to 9 MPa
HINT: The A/C switch and all accessory switches should be off, and the shift lever should be in the N or P position, and the engine should be fully warmed up.
NG -- REPAIR OR REPLACE FUEL SYSTEM FOR HIGH PRESSURE (REFER TO DTC P0087 AND P0088) P0087, P0088
OK -- Continue to next step.
19. PERFORM SYSTEM CHECK (D-4S TEST)
(a) Put the engine in inspection mode Inspection Mode Procedure.
(b) Connect the Techstream to the DLC3.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Way / Direct.
HINT: The A/C switch and all accessory switches should be off, and the shift lever should be in the N or P position, and the engine should be fully warmed up.
(e) Read the value Short FT #1, Long FT #1, Short FT #2, Long FT #2 and Fuel Pump Duty (D4).
Result:
C -- REPLACE ECM
B -- CHECK FUEL RELIEF VALVE
A -- REPLACE FUEL PRESSURE SENSOR
D -- Continue to next step.
20. PERFORM SYSTEM CHECK (D-4S TEST)
(a) Put the engine in inspection mode Inspection Mode Procedure.
(b) Connect the Techstream to the DLC3.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Way / Direct.
HINT: The A/C switch and all accessory switches should be off, and the shift lever should be in the N or P position, and the engine should be fully warmed up.
(e) Read the value Short FT #1, Long FT #1, Short FT #2, Long FT #2 and Fuel Pump Duty (D4).
Result:
D -- CHECK FOR INTERMITTENT PROBLEMS
C -- REPLACE FUEL INJECTOR FOR DIRECT INJECTION (BANK 2)
B -- REPLACE FUEL INJECTOR FOR DIRECT INJECTION (BANK 1)
A -- REPLACE FUEL INJECTOR FOR DIRECT INJECTION (ALL CYLINDER)
21. CHECK FUEL RELIEF VALVE
(a) Put the engine in inspection mode Inspection Mode Procedure.
(b) Connect the Techstream to the DLC3.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Data List / Fuel Press.
(e) Check that the fuel pressure fluctuates when the fuel hose is pressed with your fingers.
Result:
A -- REPLACE FUEL RELIEF VALVE
B -- REPLACE FUEL PUMP FOR HIGH PRESSURE
22. CHECK FUEL INJECTOR FOR PORT INJECTION
(a) Check the injection volume (whether fuel volume is high or low, and whether injection pattern is poor).
NG -- REPLACE FUEL INJECTOR FOR PORT INJECTION
OK -- REPLACE ECM