Upstream

1. Disconnect the battery ground cable.
2. Disconnect the electrical connectors from the upstream Heated Oxygen Sensors (HO2S).
3. Use Oxygen Sensor Wrench T94P-9472-A or equivalent to remove sensor(s) from exhaust manifold(s).
4. Reverse procedure to install. Tighten sensors to 30-49 Nm (22-36 lb ft).