O2 Sensor Location & Identification: Introduction

This article provides information on the proper identification of engine bank 1 and engine bank 2 for correct A/F sensor and oxygen sensor replacement.

This article contains information that identifies engine bank 1 and engine bank 2 on the following engines:

1AZ-FE, 2AZ-FE, 2AZ-FE (PZEV), 1GR-FE, 2GR-FE, 2JZ-GE, 1MZ-FE, 3MZ-FE, 1UR-FE, 3UR-FE, 2UZ-FE, 5VZ-FE, and 1ZZ-FE.

• Bank 1 (B1) refers to the bank that includes cylinder No. 1.
• Bank 2 (B2) refers to the bank opposite bank 1.
• Sensor 1 (S1) refers to the sensor that is located before the catalytic converters.
• Sensor 2 (S2) refers to the sensor that is located after the catalytic converters.