Oxygen Sensor: Tercel

1. Two oxygen sensors are used. A non-heated oxygen sensor is mounted on exhaust manifold. This oxygen sensor is referred to as bank No. 1 sensor No. 1, or front oxygen sensor. Another heated oxygen sensor is located on exhaust pipe behind catalytic converter. This oxygen sensor is referred to as bank No. 1 sensor No. 2, or rear oxygen sensor.
2. If problem exists with either oxygen sensor, heater (if equipped) or wiring circuit, a Diagnostic Trouble Code (DTC) will be stored in Engine Control Module (ECM). For diagnosis of DTC, see appropriate G - TESTS W/CODES article.
3. To test the heater on bank No. 1 sensor No. 2, disconnect electrical connector for heated oxygen sensor. Electrical connector for bank No. 1 sensor No. 2 is a Dark Gray 4-pin electrical connector located below passenger's side front seat and carpet, below center console. See Fig 7.
4. Using ohmmeter, check resistance between +B and HT terminals on electrical connector. See Fig 7. Replace heated oxygen sensor if resistance is not 11-16 ohms at 68°F (20°C).