Standard 1996 Subaru Legacy Outback 2.2l. Received obd code P0500 "Vehicle Speed Sensor A Malfunction." Is the sensor in question on top of the tranny case, near the front of the vehicle?

Whomever ran diagnostics should have told, anyone can buy a $39.00 scanner it comes with codes. If they could not tell you , perhaps someone else. All sold in North American use OBD2 codes and they are available on line. Search you code code p0500 for answer.
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https://www.yourmechanic.com/article/p0500-obd-ii-trouble-code-vehicle-speed-sensor-malfunction-by-spencer-clayton

This is a vehicle speed sensor to fix this you need to replace the sensor located in the top of the transmission (on the top of the gearbox)

According to http://repairpal.com/OBD-II-Code-P0500:

Vehicle Speed Sensor Malfunction
Symptoms

• Check Engine Light will illuminate
• Vehicle may not shift properly
• Speedometer may not operate correctly
• In some cases, there are no adverse conditions noticed by the driver
• In some cases, there may be performance problems and/or shifting problems.
• Other warning lights may come on such as the ABS light and Traction Control light.

Common Problems That Trigger the P0500 Code

• Defective Vehicle Speed Sensor
• Defective Speedometer
• Vehicle Speed Sensor wiring or connector
• Communication (CAN) bus problems
• Defective transmission or differential Vehicle Speed Sensor drive gear

Common Misdiagnoses

• Speedomter problem
• Internal Transmission problem
• ABS/Traction Control probelm
• Driveline problem

The P0500 code indicates a problems with the ABS system. If you have recently replaced wheel sensors, it sounds like one or more may be disconnected or flaky.

From datsc.com:
What does this mean? OBD Code P0500refers to
Basically this means that the vehicle's speed as read by the Vehicle Speed Sensor (VSS) is not working properly.
Symptoms Possible sumptoms of OBD code P0500
loss of anti-lock brakes the "anti-lock" or "brake" warning lamps on the dash may be lit the speedometer or odometer may not work properly (or at all) your vehicle's RPM limiter may be decreased the shifting of an automatic transmission may become erratic other symptoms may also be present
Causes Possible causes of OBD code P0500
A code P0500 may mean that one or more of the following has happened: The Vehicle Speed Sensor (VSS) is not reading (functioning) properly There is a broken/frayed wire leading to the vehicle speed sensor The vehicle's PCM is not correctly configured for the actual tire size on the vehicle
Possible Solutions The simplest thing to do is to reset the code and see if it comes back. Next, check all wiring and connectors that lead to the speed sensor. The location of the sensor depends on your vehicle. The sensor could be on the rear axle, transmission, or perhaps the wheel hub (brake) assembly. If the wiring and connectors are OK, then check the voltage at the speed sensor. Again, the exact procedure will depend on your make and model of vehicle. If everything looks OK, replace the sensor.

Google your codes & read up on the issues

Type: OBD & your codes

Codes do not indicate the need to replace parts

All parts have to be component tested,thus a repair
shop will be needed

P0500 is Vehicle Speed Sensor A Malfunction

There are actually two Vehicle Speed Sensors (VSS). I'm going to assume you have a 2.5 liter engine and an automatic transmission.

The Vehicle Speed Sensor 1 (output shaft rotation sensor) is mounted to the extension case (from the outside of the case). The sensor outputs a pulse signal which is transmitted to the TCM where it is converted to vehicle speed.

The transfer clutch drum is connected directly to the rear wheel driving propeller shaft. Vehicle speed sensor 1 on the AWD model detects rear-wheel speed.

Vehicle Speed Sensor 2 provides vehicle road speed information to the ECM. The ECM uses this data to properly determine ignition and fuel delivery curves. The sensor consists of a reed switch and magnetic rotor turned by the speedometer cable.

One rotation of the magnetic rotor opens and closes the reed switch four times, producing a digital signal which is converted to vehicle speed by the ECM. The sensor operates whenever the vehicle is moving with ignition ON. As the transmission rotates, the speed sensor sends a pulsed on/off signal to the ECM.

The speedometer uses VSS 2 for it's signal.

Hope this helps (remember to rate this answer).

P1540 VSS(vehicle speed sensor) signal to high, P0500 vehicle speed sensor malfunction.

P0170 Fuel Trim Malfunction (Bank 1), could be fuel filter, mass air sensor, or low fuel pressure.

They are not the sensors you want. The car uses the abs wheel sensors for vehicle speed. Your problem lies in the abs system , possibly the left front sensor, abs ecu or speedo cluster, Clear the code and see if it stay out otherwise you'll need to go to a trusted technician. .