You did not specify which O2 sensor it is. Is it sensor 1 bank 1, sensor 2 bank 2, sensor 2 bank 1, or sensor 1 bank 2. There are four O2 sensors on a Mazda 626
the sensor is located right behind the thermostat housing on your intake manifold on the drivers sided toward the front of the car.
Screwed into the lower intake manifold right at the center of the engine in front.
It is located on the front side of the engine on the transmission side. It screws in right behind the front exhaust manifold where the manifold bolts to the crossover pipe.
in the exhaust pipe right under the manifold it is easy to get to right in front under the hood
It is located on the front of the engine right by the distributor on the manifold. It has one wire right on the top of it.
it should be the bank facing the front of the car in the manifold. you should be able to find it right in front when open the hood
It is on the top back right side of the intake manifold. with you standing in the front of engine.
It is located on the front edge of the drivers side head, right above the exhaust manifold.
upstream 02 sensor located right above exhaust manifold gasket downstream located right in front of catallytic converter
coolant temp. sensor- front of motor on intake manifold intake air temp. sensor- right side of throttle body, on valve cover i believe
There is a coolant temperature sensor and a temperature gauge sensor. the coolant sensor is located on driver side of the cylinder head. screws right into it, and the temperature gauge sensor is on the front side of the cylinder head right under the distributor. hope this helps
On the right rear of the exhaust manifold ( behind the exhaust manifold) , you will have to turn the engine to get to it . (* check out chilton manaul for 98-? for vans and trucks .