There are 3. One you can see by looking down on the upper right of the engine. It is screwed onto the manifold and connects to a plug in jack in the back middle. The rest are sadly under the car. I have the same problem right now.
http://ww2.justanswer.com/uploads/djenn434/2009-12-11_151704_cat_0000.jpg
right in the motor!
Inside the distributor.
The automatic transmission temperature sensor, on your 1990 Mitsubishi, is located on the top of the transmission. The sensor will have to electrical wires going to it.
in the transmission
manifold differential pressure sensor montero sport 3.0
There are two oxygen sensor for Mitsubishi Outlander. Front Oxygen Sensor and Rear Oxygen Sensor
There are two MAP Sensors on the Mitsubishi Montero Limited. They are both located on the left side of the engine about six inches apart. Look for a plug with a wire attached that resembles a spark plug wire boot.
manifold differential pressure sensor montero sport 3.0
Bank 1 is before the CAT and on the left side (driver side) by the manifold.
speed sensor location Mitsubishi montero 94 ls, 3.0
where is an oxygen sensor in 2000 mitsubishi pajero io
where is the oxygem sensor on 1996 Mitsubishi mirage