Toyota 2GR-FE Manual page 355

DTC P0171
DTC P0172
DTC P0174
DTC P0175
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.
DTC No.
With warm engine and stable air-fuel ratio feedback,
P0171
fuel trim considerably in error to lean side (2 trip
P0174
detection logic)
With warm engine and stable air-fuel ratio feedback,
P0172
fuel trim considerably in error to rich side (2 trip
P0175
detection logic)
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.
2GR-FE ENGINE CONTROL SYSTEM – SFI SYSTEM
System Too Lean (Bank 1)
System Too Rich (Bank 1)
System Too Lean (Bank 2)
System Too Rich (Bank 2)
DTC Detection Conditions Trouble Areas
• 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 sensor heater relay
• A/F sensor heater and A/F sensor heater relay
circuits
• PCV valve and hose
• PCV hose connections
• ECM
• 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 sensor heater relay
• A/F sensor heater and A/F sensor heater relay
circuits
• ECM
ES–199
ES