Poor gas mileage, poor performance and inability to pass an emissions test can all mean that the oxygen sensors in a Mazda MPV 2000 have failed. It is a good idea to connect an OBD-II scanner to the MPV to make sure the the problem is caused by a bad oxygen sensor before purchasing replacements because the 2000 MPV has four sensors, and this can get expensive.
Disconnect the negative battery cable from the battery by loosening the locking nut with an adjustable wrench and pulling the cable off the battery post.
Disconnect the oxygen sensor located on the left side of the exhaust manifold (toward the grill of the engine compartment where the exhaust system joins the engine block) from the engine electrical system. Press in the tabs on the sides of the connecting plug and separate the sensor wires from the electrical harness.
Trace the sensor wires to the sensor that is inserted into the manifold pipes and spray the nut with penetrating lubricant. Wait 2 minutes for the lubricant to work, then remove the sensor using an adjustable wrench to turn the nut counterclockwise until you can pull the entire sensor out of the manifold.
Insert the new sensor into the manifold and tighten it into place by turning the nut clockwise with an adjustable wrench until it is hand tight.
Connect the new sensor to the engine electrical system by pushing the connector from the sensor into the receiver on the electrical harness.
Repeat the process used to change the first sensor for the second sensor. The second sensor is located top of the exhaust manifold (where the exhaust systems joins the engine block) to the rear of the engine compartment. Disconnect the sensor from the electrical harness and remove the sensor. Install and connect the new sensor.
Repeat the process used to change the first sensor for the third sensor. The third sensor is located top of the exhaust pipe just below where the two pipes (one from each manifold) join into one pipe leading to the catalytic converter. Disconnect the sensor from the electrical harness and remove the sensor. Install and connect the new sensor.
Repeat the process used to change the first sensor for the fourth sensor. The fourth sensor is located top of the exhaust pipe just after the catalytic converter (the wider section of the exhaust pipe between the manifolds and the muffler). The sensor is on the portion of the pipe nearer to the muffler at the end. Disconnect the sensor from the electrical harness and remove the sensor. Install and connect the new sensor.
Reconnect the negative battery cable to the battery and tighten the lock nut with an adjustable wrench until it is hand tight.
