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

WARNING: This page is about a different car, the 2003 Lexus LX 470. However, it is still accessible from the selected car via links, so may be relevant.

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)

NOTE: For information on engine immobilizer system, see COMPUTERIZED ENGINE CONTROLS in THEORY & OPERATION article.

CAUTION: If ECM replacement is instructed in following testing, always ensure ECM harness connector 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.

NOTE: Bank No. 1 refers to bank which includes cylinder No. 1. Bank No. 2 refers to bank without cylinder No. 1. Heated oxygen sensor No. 1 refers to sensor closest to engine block.