Tacoma Except Calif. Emission Vehicles & 4Runner Except Calif. Emission Vehicles

A heated oxygen sensor is mounted on exhaust pipe in front of catalytic converter. This oxygen sensor is referred to as bank No. 1 sensor No. 1, or front oxygen sensor. Another heated oxygen sensor is mounted on exhaust pipe behind catalytic converter. This oxygen sensor is referred to as bank No. 1 sensor No. 2, or rear oxygen sensor.
To test heater resistance on any oxygen sensor, disconnect electrical connector for appropriate heated oxygen sensor. Using ohmmeter, check resistance between +B and HT terminals on electrical connector. See Fig 1-Fig 4 . Replace heated oxygen sensor if resistance is not 11-16 ohms at 68°F (20°C) and 23-32 ohms at 1472°F (800°C).
If problem exists in either heated oxygen sensor, heater or wiring circuit, a Diagnostic Trouble Code (DTC) may be stored in Engine Control Module (ECM). See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article for retrieving and servicing of DTCs.

Fig 1: Locating Electrical Connector & Testing Bank No. 1 Sensor No. 2 Oxygen Sensor (Tacoma)

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Fig 2: Locating Electrical Connector & Testing Bank No. 1 Sensor No. 2 Oxygen Sensor (4Runner)

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Fig 3: Locating Electrical Connector & Testing Bank No. 1 Sensor No. 1 Oxygen Sensor (Tacoma Except Calif. Emission Vehicles)

Fig 4: Locating Electrical Connector & Testing Bank No. 1 Sensor No. 1 Oxygen Sensor (4Runner Except Calif. Emission Vehicles)