carnac, automotive stores sell an offset wrench (basically an open end wrench with a slot) for installation/removal of Oxygen sensors. The wrench costs around $10 and fits over the electrical lead. Remove the passenger side carpet insert and unplug the electrical lead. From below the car push the grommet into the passenger compartment so the electrical lead is free and clear. Then unscrew the Oxygen sensor and remove. Installation of new Oxygen sensor is reverse order. Make sure there is a coating of Never-Seeze on the Oxygen sensor threads ... makes removal the next time much easier.

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Fred Hoelzle