Lexus IS250 IS220d GSE20 ALE20 4GR-FSE ENGINE CONTROL SYSTEM
CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0171, P0172, P0174 OR P0175)
PERFORM ACTIVE TEST BY INTELLIGENT TESTER (A/F CONTROL)
READ VALUE OF ENGINE COOLANT TEMPERATURE SENSOR (COOLANT TEMP)
READ VALUE OF INTAKE AIR FLOW METER (MAF)
CHECK FUEL PRESSURE (LOW PRESSURE SIDE)
CHECK FUEL PRESSURE (HIGH PRESSURE SIDE)
INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)
CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM)
PERFORM CONFIRMATION DRIVING PATTERN
CHECK WHETHER DTC OUTPUT RECURS (DTC P0171, P0172, P0174 OR P0175)
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 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.
| DTC No. | DTC Detection Condition | Trouble Area |
| P0171 P0174 | With warm engine and stable air-fuel ratio feedback, fuel trim considerably in error to lean side (2 trip detection logic) | Air induction system Injector blockage Mass Air Flow (MAF) meter Engine Coolant Temperature (ECT) sensor Fuel pressure Gas leakage from exhaust system Open or short in A/F sensor (bank 1, 2 sensor 1) circuit A/F sensor (bank 1, 2 sensor 1) A/F sensor heater (bank 1, 2 sensor 1) A/F HTR relay A/F sensor heater and A/F HTR relay circuits PCV valve and hose PCV hose connections ECM |
| P0172 P0175 | With warm engine and stable air-fuel ratio feedback, fuel trim considerably in error to rich side (2 trip detection logic) | Injector leakage or blockage MAF meter ECT sensor Ignition system Fuel pressure Gas leakage from exhaust system Open or short in A/F sensor (bank 1, 2 sensor 1) circuit A/F sensor (bank 1, 2 sensor 1) A/F sensor heater (bank 1, 2 sensor 1) A/F HTR relay A/F sensor heater and A/F HTR relay circuits ECM |
- HINT:
WIRING DIAGRAM
Refer to DTC P2195
INSPECTION PROCEDURE
- HINT:
- Intelligent tester only:
- Malfunctioning areas can be identified by performing the A/F CONTROL function provided in the ACTIVE TEST. The A/F CONTROL 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 A/F CONTROL operation using an intelligent tester.
- HINT:
| Tester Display (Sensor) | Injection Volume | Status | Voltage |
| AFS B1S1 or AFS B2S1 (A/F) | +25 % | Rich | Less than 3.0 |
| AFS B1S1 or AFS B2S1 (A/F) | -12.5 % | Lean | More than 3.35 |
| O2S B1S2 or O2S B2S2 (HO2) | +25 % | Rich | More than 0.55 |
| O2S B1S2 or O2S B2S2 (HO2) | -12.5 % | Lean | Less than 0.4 |
- 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.
| Case | A/F Sensor (Sensor 1) Output Voltage | HO2 Sensor (Sensor 2) Output Voltage | Main Suspected Trouble Area | ||
| 1 | Injection Volume +25 % -12.5 % |  | Injection Volume +25 % -12.5 % | | - |
| Output Voltage More than 3.35 V Less than 3.0 V |  | Output Voltage More than 0.55 V Less than 0.4 V |  | ||
| 2 | Injection Volume +25 % -12.5 % | | Injection Volume +25 % -12.5 % | | A/F sensor A/F sensor heater A/F sensor circuit |
| Output Voltage Almost no reaction |  | Output Voltage More than 0.55 V Less than 0.4 V | | ||
| 3 | Injection Volume +25 % -12.5 % | | Injection Volume +25 % -12.5 % | | HO2 sensor HO2 sensor heater HO2 sensor circuit |
| Output Voltage More than 3.35 V Less than 3.0 V | | Output Voltage Almost no reaction | | ||
| 4 | Injection volume +25 % -12.5 % | | Injection Volume +25 % -12.5 % | | Injector Fuel pressure Gas leakage from exhaust system (Air-fuel ratio extremely lean or rich) |
| Output Voltage Almost no reaction | | Output Voltage Almost no reaction | | ||
- HINT:
| 1.CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0171, P0172, P0174 OR P0175) |
Connect the intelligent tester to the DLC3.
Turn the engine switch on (IG) and turn the tester ON.
Enter the following menus: Power train / Engine / DTC.
Read DTCs.
- Result:
Display (DTC output) Proceed to P0171, P0172, P0174 or P0175 A P0171, P0172, P0174 or P0175 and other DTCs B
- HINT:
- If any DTCs other than P0171, P0172, P0174 or P0175 are output, troubleshoot those DTCs first.
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| 5.READ VALUE OF ENGINE COOLANT TEMPERATURE SENSOR (COOLANT TEMP) |
Connect the intelligent tester to the DLC3.
Turn the engine switch on (IG) and turn the tester ON.
Enter the following menus: Power train / Engine / Data List / Coolant Temp.
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)
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