DTC P0171, DTC P0172, DTC P0174 Or DTC P0175: System Too Lean/Rich: Notes

WARNING: This page is about a different car, the 2002 Toyota MR2. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: DTC P0171 indicates system too lean (bank No. 1). DTC P0172 indicates system too rich (bank No. 1). DTC P0174 indicates system too lean (bank No. 2). DTC P0175 indicates system too rich (bank No. 2).

NOTE: These DTCs may be caused by the vehicle running out of fuel.

CAUTION: If ECM replacement is instructed in following testing, always ensure ECM connectors and ground circuits are okay. If either are defective, 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 - IMPORT - IMPORT article in GENERAL INFORMATION, or appropriate ENGINE IMMOBILIZER SYSTEMS article in ACCESSORIES & EQUIPMENT.

NOTE: Heated oxygen sensor for cylinders No. 1 and 4 is referred to as bank No. 1 sensor No. 1 and is located at timing chain of exhaust manifold above catalytic converter. Heated oxygen sensor for cylinders No. 2 and 3 is referred to as bank No. 2 sensor No. 1 and is located at flywheel end of exhaust manifold, above catalytic converter.

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