I brought my truck to my mechanic to get a few things replaced on it. The ABS light has been on and he ran it through 2 of his computers and no code was popping up for him. He checked all the fuses which we also good.

I did some searching on here and it seems like it could possibly be the ABS sensor. Is there anyway to tell if the sensor on the rear axle or the one in front is faulty?

Would there be another reason the ABS light would be stuck on? I have regular brakes still. My break fluid reservoir is full, as someone on these forums said could be the culprit.

 

There is a fluid level sensor on the Brake Master cylinder, unplug its wires and check for corrosion, clean connections.
Make sure Brake lights work.

Pull out the Rear axle sensor and check its tip, make sure there is no damage, also check connections for corrosion.

Rear axle VSS sensor is just used for ABS in 1997, it is a Variable Reluctance(VR) sensor, this means it generates its own AC Voltage when axle is spinning.
You could test with OHM meter but there is no "correct OHMs", only incorrect which would be No Connection inside the sensor.
You could jack up the rear axle and hook volt meter up, set it for AC volts
Spin a wheel and you should see AC Volts start to go up, faster you spin the higher the volts, but it would still only be .5vAC to 1.5vAC so not high voltage.

Rear axle sensor is not very expensive, $10-$15, so some just change it on spec, to save the time of testing it, or pick one up at wrecking yard

ABS is a passive system so can't effect braking much, and Rear wheel only ABS is very passive, rear wheels can still lock up on loose gravel or wet roads if bed is empty.
Rear wheel ABS has a valve on the 1 rear brake line that feeds both rear wheels, if VSS "speed"/voltage drops too quickly, i.e. axle lockup, then ABS module will pulse that valve which reduces pressure in that 1 rear brake line which keeps slaves from pushing shoes to hard on the drums
But it can't stop all pressure, it can't prevent braking
When ABS is active during wheel lock up you will feel a pulsing in the brake pedal, that's the valve changing position rapidly to lower pressure to rear wheels

Just FYI
Rangers use a 2 reservoir Master, one for front brakes and one for rear brakes, both are filled when brake fluid it topped up, but if there is a leak in either front or rear brake lines both reservoirs won't be drained, only the leaking one would be, so you won't lose all braking.
Pedal would be soft and sink to the floor because of the leak but non-leaking lines would brake the vehicle as you pumped the pedal, I know because it has happened to me, lol.

 

Thank you very much for the info. I might just switch out the sensor.

I should know this, but I don't. Do I have ABS braking in the front? Should I replace that sensor as well?

 

In 1997 no probably not.
You can turn front wheels all the way one direction then look behind the wheel at back of "axle"/spindle you will see the rubber brake line going into the caliper, just below that there would be a wiring harness with two wires in it for the ABS sensor on that one wheel
Each front wheel would have one for 4WABS, 4 wheel ABS