Originally posted by G Pappas:
..I believe that the front two sensors are a little different than the back two.
Perhaps ambiguous. Upstream (front) are before catalytic in manifold, downstream (back) are after catalytic in manifold.
The sensor of concern is on the exhaust manifold behind rad and to the right of oil filter. It is possible to change without an O2 sensor socket by using an open end wrench.
