Vehicle speed sensor

Fat as possible.

It is located on the transmission casing, it is easy to see. Picture of sensor below. I assume this is the Vehicle Speed Sensor (VSS)

The following fixya link tells how to change and where to find the vss How to replace the speed sensor on 2000 mercury villager

go under the car, go to the center of the firewall, look up, you can not see the sensor very well, if you buy the new one so you will know what you are looking for.

Have you ran an Oil pressure test? low oil pressure (20lb)or no oil pressure(0lb)and the lifters will not open the valves enough to let fuel in to the cylinder to start your engine!

2.0L is on the lower rear of transaxle. 2.5L is on the right side of the transaxle.

I just got done replacing the O2 sensors in my 99 Cougar due to throwing a P0135 malfunction code. There's 3. Facing the engine there's one in the front coming off of the front header, which is easy to get to. Another more tricky one if between the engine and the fire wall on the rear header pipe. The third is under the vehicle behind the transmission pan on top of the exhaust. In order to replace the O2 sensor near the fire wall you will need to remove the 4 retaining bolts for the ECM module and move it out of the way. Additionally you will need to remove the 2 retaining nuts for a wiring harness that is seated below the ECM module. Pay close attention to the connectors because the front and under vehicle O2 sensors have round connectors the one near the firewall has a squared connector. I was able to replace all 3 by myself in approximately 35 minutes. If your throwing a O2 heater malfunction code it is most likely going to be the sensor near the firewall. make sure that you know someone with a code reader so the code can be cleared. If you're do for an emmissions inspection be sure to put at least 40 miles on the new O2 sensor with different types of driving (e.g. highway, coasting, decellerated turns and rapid acceleration). Gotta love project cars for your kids!!

v6 or 4 cylinder?

SECTION 303-01A: Engine - 2.0L 1999 Cougar Workshop Manual
IN-VEHICLE REPAIR Valve Cover Removal

1. Disconnect the oil feed sensor electrical connector.

1. Disconnect the crankcase ventilation tube.

1. Remove the appearance cover.
   1. Position the throttle cable out of the way, and the speed control cable (if equipped).
   1. Remove the eight bolts.
   1. Remove the appearance cover.

1. Remove the spark plug wires.

1. Detach the upper part of the engine front cover out of the way.
   1. Remove the four bolts.
   1. Position the front cover to one side.

1. Remove the valve cover.
   1. Position the throttle cable to one side, and the speed control cable (if equipped).
   1. Remove the nine bolts.
   1. Remove the valve cover

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here is illustration. 1 bolt holds it in. VSS sends vehicle speed information to computer so it can determine shift timing, fuel input, etc.