With M/T

NOTE: This article contains corrected data processed from TSB# PG001-05.

DTC P0171 System too Lean (Fuel Trim) (Only for M/T)(Bank 1)
DTC P0172 System too Rich (Fuel Trim) (Only for M/T)(Bank 1)
DTC P0174 System too Lean (Fuel Trim) (Only for M/T)(Bank 2)
DTC P0175 System too Rich (Fuel Trim) (Only for M/T)(Bank 2)

DTC Detecting Condition:

Wiring Diagram:

CIRCUIT DESCRIPTION
Fuel trim is related to the feedback compensation value, not to the basic injection time. Fuel trim includes short-term fuel trim and long-term fuel trim.

Short-term fuel trim is the short-term fuel compensation used to maintain the air-fuel ratio at its ideal theoretical value. The signal from the heated oxygen sensor indicates whether the air-fuel ratio is RICH or LEAN compared to the ideal theoretical value, triggering a reduction in fuel volume if the air-fuel ratio is rich, and an increase in fuel volume if it is lean.

Long-term fuel trim is overall fuel compensation carried out long-term to compensate for continual deviation of the short-term fuel trim from the central value due to individual engine differences, wear overtime and changes in the usage environment.

If both the short-term fuel trim and long-term fuel trim are LEAN or RICH beyond a certain value, it is detected as a malfunction and the MIL lights up.

HINT:
- When DTC P0171 or P0174 is recorded, the actual air-fuel ratio is on the LEAN side. When DTC P0172 or P0175 is recorded, the actual air-fuel ratio is on the RICH side.
- If the vehicle runs out offuel, the air-fuel ratio is LEAN and DTC P0171 or P0174 is recorded. The MIL then comes on.
- If the total of the short-term fuel trim value and long-term fuel trim value is within ±35 % (80°C (176°F) or more), the system is functioning normally.

INSPECTION PROCEDURE

HINT: Read freeze frame data using TOYOTA hand-held tester or OBD II scan tool, as freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.

Step 1:

Steps 2 - 6:

Steps 7 - 9:

Steps 10 - 11: