DTC P0171, DTC P0172, DTC P0174 & DTC P0175: Notes

WARNING: This page is about a different car, the 2003 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION: If ECM replacement is instructed in following testing, always ensure ECM connectors and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. If ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system. For programming procedures, see COMPUTER RELEARN PROCEDURES - LEXUS article in GENERAL INFORMATION.

NOTE: Bank No. 1 is also know as right bank (RH). A/F sensor refers to sensor closest to engine block.

NOTE: For component location, see appropriate illustration in THEORY & OPERATION article.

Code Definition

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)